A STUDY OF THE TIME REQUIRED BY STUDENTS OF VOCATIONAL AGRICULTURE FOR PRACTICE TO DEVELOP BASIC SKILLS IN ARC WELDING by Adolphus James Miller An Abstract Submitted to the School of Advanced.Graduate Studies of Michigan State University of Agriculture and Applied Science in partial fulfillment of the Requirements for the Degree DOCTOR OF EDUCATION Department of Vocational Education 1955 Approved 1,.[0' ‘54 Adolphus James Miller A STUDY OF THE TIME REQUIRED BY STUDENTS OF VOCATIONAL AGRICULTURE FOR PRACTICE TO DEVELOP BASIC SKILLS IN ARC WELDING ‘2332233.- To find answers to the questions, (1) How much time do students of vocational agriculture require for practice to deveIOp these basic skills in arc welding; making a bead, making a fillet ' weld, making a butt weld, and making a fillet-weld lap Joint? (2) Is the time that students require for practice to develop skills in arc'welding associated with the age of the students? (3) Is there a difference between the time required for practice to develop the skills by those students who were without knowledge of arc welding and that required by those students who had knowledge of arc 'welding? (b) Is the time that students require for practice to develop skills in arc welding associated‘with the time used by teachers to demonstrate the skills? (5) Is there a difference be- tween the time required for practice to develop skills in arc welding by those students who began practicing the same day the demonstration was given and that required by students who did not begin practicing the same day the demonstration was given? Method.- The author developed an instrument for gathering data to determine the practice-time required to develop four skills in arc welding. In 1953, fortyathree teachers used the instrument Adolphus James Miller with one hundred ninety-five students in the States of Illinois, Michigan, North Carolina, Ohio and Virginia. The teachers used the instrument as a guide to demonstrate the skills and the pupils used it as a guide while practicing. The practice-time in minutes re- quired by students to develOp each skill constituted the major part of the data. Mg and interpretations.- It was found that: (1) The mean practice—times in minutes required to develop the skills were; 50.32 t 5.10 for making a bead, 1.8.37 is 5.h7 for making a fillet weld, h0.h8 t 3.92 for making a butt weld, and 35.33 t 3.79 for making a fillet-Ileld lap joint. (2) There were no significant dif- ferences among the means of the practice-time of the five age groups to develop any one of the skills. (3) Students who gained knowledge of arc welding through observation but without practice did not, on an average, develop the basic skills with any less practice than students who had not gained such knowledge. ()4) Teachers cannot be sure of reducing the time required by students to develop skills in arc welding by giving longer demonstrations. (5) When the mean number of days between the demonstration and the day the students begin practicing is no greater than four it can be reasonably ex- pected that students will develop skills in arc welding as quickly as those who began practicing the day the demonstration was given. Adolphus James Miller It is recommended that: (1) Class schedules be arranged and welding facilities and supplies provided that will allow each student approximately 175 minutes for practice and permit him to begin practicing each skill within four days after it has been demonstrated. (2) Arc welding skills he taught to any age group enrolled in highpschool or young farmer classes. (3) The method of collecting data be used to further determine the time required to develop skills in arc welding and other areas of farm mechanics. A STUDY OF THE TIME REQUIRED BY STUDENTS OF VOCATIONAL AGRICULTURE FOR PRACTICE TO DEVELOP BASIC SKILLS IN ARC WELDING by Adolphus James Miller A Thesis Submitted to the School of Advanced Graduate Studies of Michigan State University of Agriculture and Applied Science in partial fulfillment of the Requirements for the Degree DOCTOR OF EDUCATION Department of Vocational Education 1955 ACKNOWLEDGMENTS The writer wishes to express his sincere appreciation to all who have assisted in making this study possible. For his critical analysis and careful guidance during the study, the writer wishes to express genuine appreciation to his Major Professor, Dr. Harold M. Byram. To Mr. Carl Albrecht, of the Agricultural Engineering Department, Michigan State University, to Mr. Robert 0. Harris, formerly of the Agricultural Engineering Department, Virginia State College and to the four teachers of Vocational Agriculture sincere thanks are extended for trying out the instrument prepared for the study, critically evaluating it and offering suggestions for its improvement. I Special recognition and grateful appreciation are extended to the teachers and students of vocational agriculture who utilized their time and effort to participate in the study. Sincere thanks are extended to Dr. Kenneth J. Arnold, Department of mathematics, Michigan State University, for his advice on the selection of statistical methods and techniques used, and.to Dr. Alonzo Myster, Director of the Statistical laboratory, Virginia State College, for his interest, suggestions and assistance with the statistical procedures used in the study. To his wife and daughter the writer is eternally thankful for their confidence, patience and stimulation which made this study possible. TABLE OF CONTENTS CHAPTER I. INTRODUCTION.............. Statement of the problem . . . . . . Background for the study . . . . . . Scopeofthestudy . . . .. . . . . Limitations of the study . . . . . . Basic assumptions . ... . . . . . . DefinitionofTerms . . . . . . . . . Plan of Organization . . . . . . . . . II. REVIEWOF RELATED LITERATURE . . . . . . Instrument for Gathering Data . . . . Skills and Their Develoment . . . . . The Used for Learning How to Weld . . Summary ............... III. METHOD OF INVESTIGATION . . . . . . . . Preliminary Activities . . . . . . . . Preparation of the Instrument . . . . Instructions to the teacher . . . . Jobbreakdown ........... Classification of trainees and record Instructions for trainees . . . . . Pilot studies of the instrument . . of time 30 31 32 32 33 35 35 CHAPTER Collecting the Data . . . . . . . Selection of the states . . . . Selection of the teachers . . . Hailing the instrument . . . . Recording the data . . . . . . . Second sample . . . . . . . . . Method Used in Analyzing the Data Analysis of variance . . . . . That-test .....,..... Coefficient of correlation . . IV. PRESENTATION AND ANALYSIS OF DATA . Distribution of Trainees . . . . Age of Trainees and PracticeJTime Making a bead . . . . . . . . flaking a fillet weld . . . . . Making a butt weld . . . . . . Making a filletdueld lap joint Discussion and interpretation . Trainees' Knowledge of Arc‘welding time . . . . . . . . . . . . . ‘Haking a bead . . . . . . . . . Making a fillet'weld . . . . . Making a.butt weld . . . . . . Making a filletaweld lap joint and Practice- PAGE 36 36 37 37 38 38 39 1:3 h? h? 52 52 SS 57 61 68 7O 73 CHAPTER The Day the Trainees Began Practicing and the IPractice—Time Makingabead ................ Makingafilletweld . . . . . . . . . . . . Makingabuttweld ............. Making a fillet-weld lap joint . . . . . . . Discussion and interpretation . . . . . . . . Relationship of the Practice-Time Required by Trainees to Develop Skills and the Time Used by Teachers to Demonstrate the Skills . . . . Practice-Time of the First Sample Compared with thatoftheSecondSample . . . . . . . . . . Practice-Time Required to Develop Four Skills . Reliability and Validity of the Method . . . . Validity ...-............... SW C O O O O O O O O O O O O O O i. C O O O V. SUMMARY AND CONCLUSIONS SW C O O O O O O O O O O O O O O O O O O com1u31ons O O 0 O O O O O O O O O O O O O O B ELI mm 0 O O O O O O O O O O O O O O O O O O O O O O APPENDICES PAGE 73 75 76 78 81 83 86 88 9O 91 92 95 97 102 106 TABLE II. ‘ III . VII. VIII . LIST OF TABLES Trainees and Teachers who Participated in the StudybyStates ............... Trainees Grouped in Terms of the Number Taught bythesameTeacher .......... AgesofTraineesinIears . . . . . . . . . . . Practice-Time in Minutes Required by Five Age Groups to Develop the Ability to Make a Bead withtheArcWelder ............. Analysis of Variance of Practice-Time in Minutes used by Trainees in Five Age Groups to Develop the Ability to Make a Bead with the Arc Welder Prmtice-Time in Minutes Required by Five Age Groups to Develop the Skill Making a Fillet Weldwiththe ArcWelder . . . . . . . . . . Analysis of Variance of Practice-Time in Minutes used by Trainees in Five Age Groups to Deve10p the Ability to Make a Fillet Weld with the Arc Welder.................... Practice-Time in Minutes Required by Five Age Groups to DeveIOp the Skill Making a Butt Weld withtheArcWelder ............. PAGE 158 h9 50 53 SS 56 58 59 TABLE II. III . XIII. PAGE Analysis of Variance of Practice-Time in Minutes used by Trainees in Five Age Groups to Develop the Ability to Make a Butt Weld with the Arc Welder ..................... 60 The Practice-Time in Minutes Required by Five Age Groups to Develop the Skill Making a Fillet-Weld LapJoint ................... 62 Analysis of Variance of Practice-Time in Minutes used by Trainees in Five Age Groups to Develop the Ability of Making a Fillet-Weld Lap Joint withtheArcWelder .............. 63 Significance of the Difference between Means of the PracticedTime Used to DeveIOp Four Skills in Arc Welding by Fifty-five Trainees who were Without Knowledge of Arc Welding and Seventy-four Trainees'Who had Knowledge of Arc welding - FirstSample .................. 69 Significance of the Difference between Means of the Practice-Time Used to Develop Four Skills in Arc Welding by Twenty—nine Trainees who were Without Knowledge of Arc Welding and Thirtyaseven Trainees Who had Knowledge of Arc Welding - SecondSample ................. 72 TABLE PAGE XIV. Significance of the Difference between Means of the Practice-time Required to Develop Four Skills in Arc Welding by Trainees Who began Practicing the Day the Demonstration was Given and Trainees Who did not Begin Practicing the Day the Demonstration was Given - First Sample ..................... 77 IV. Significance of the Difference between Means of the Practice-time used to Develop Four. Skills in Arc Welding by Trainees Who Began Practicing the Day the Demonstration was Given and Trainees Who did not Begin Practicing the Day the Demonstration was Given -— Second Sample . . . . 79 XVI. Coefficients of Correlation between the Practice- time in Minutes Used by the Trainees to Deve10p the Ability to Perform Four Skills in Arc Welding and the Time Used by the Teachers to . Demonstrate the Skills and the Test of Signifi— canceofr.................. 85 XVII. Significance of the Difference between Means of the Practice-time Used to Deve10p Four Skills in Arc Welding by Trainees in the First Sample and Trainees in the Second Sample . . . . . . 87 TABLE PAGE XVIII. Mean Practice-time in Minutes Required by 195 Trainees to Develop Four Skills in Arc Welding.....'............... 89 CHAPTER I INTRODUCTION Statement g£_the problem. The major problem of this study was to find an answer to the question, How much time do students of voca- tional agriculture require for practice to develop four basic skills in arc welding? Subsidiary problems of the study were: 1. 3. Is the time that students require for practice to develop the skills in arc welding associated with the age of the students? Is there a difference between the time required for practice to develop the skills by those students who were without knowledge of arc welding and that required by those students who had knowledge of arc welding? Is the time that the students required for practice to develop the skills in arc welding associated.with the time used by the teachers to demonstrate the skills? Is there a difference between the time required for practice to develop the skills in arc welding by those students who began practicing the same day the demonstration was given and that required by those who did not begin practicing the same day the demonstration was given? Is the method that was used to collect data for the study reliable and valid? Backggpund for the study. There is need for a better estimate of the time required by students of vocational agriculture for practice to develop the basic skills in arc welding and other farm mechanics jobs. This need has been intensified by the rapid advance- ment in mechanized farming andthe use of arc welders by farmers and prospective farmers to construct labor-saving equipment, and maintain and repair machinery on their farms. .Also, some farm mechanics classes are operated in schools that have schedules organized on the sixty- minute period basis. The problem of finding sufficient time to teach manipulative skills is encountered in such schools. This is true because much of the students' time must be used to get their tools and materials ready before they can‘begin.their jobs and they must return the tools and unused materials to their proper places before the class period ends, hence, little time is left for demonstrations and practice of new skills. Farm.mechanics instruction is available for prospective farmers and farmers of ages above fourteen years. Some authorities feel that there is probably a manipulative skill readiness stage in the develOpment of an individual. If this is true, there is a stage at which arc welding skills can be developed more readily by students in farm.mechanics. Much time can.be saved if arc welding skills are taught to the students after this readiness stage has been reached. ' Wdth this thought in mind the author attempted to find if the students of different age levels in this study used different amounts of practice- time to develop the arc welding skills. In.many farm.mechanics classes before the students have received systematic instruction in arc welding they have had an opportunity to observe and study the welding operations and jobs that other individuals are performing. Through such media some knowledge is gained. One might form the hypothesis that individuals who have gotten knowledge from such sources would develop arc welding skills with less practice- tims than those persons who have not had these or similar experiences. It was decided that one of the purposes of this study should be to provide some factual information with regards to this hypothesis. The demonstration is considered the most effective method of teaching manipulative jobs by many authorities in farm.mechanics instruction. In many departments of vocational agriculture where arc welding is taught there is only one welder, therefore, only one student can practice at a time. When arc welding demonstrations are given to a class or to a group within a class several days usually ‘will have passed before all members have had an opportunity to prac- tice the skill that was demonstrated. This situation has created interest in this question: Do the students who begin their practice periods immediately after the demonstration is given develop the ability to perform the skills in less time than those who do not begin practicing immediately after the demonstration? It seemed appropriate that another of the purposes of this study should be to provide some factual information to help answer this question. The primary aim.of vocational education in agriculture is, 'to train present and prospective farmers for proficiency in farming.'1 Arc welding and other farm mechanics activities must be taught in a highly efficient manner if they are to develop the student's proficiency. To have teaching programs that attain the aim of vocar tional education in agriculture, administrators and teachers must plan schedules and provide equipment that are adequate. The teacher or administrator who wishes to plan an adequate schedule may ask, "How many and what length periods are needed for students to practice in order to develop the farm.mechanics skills included in the courses for this department?" The teacher or administrator who wishes to make ,plans that provide adequate equipment in the school shop may ask, ”How manwaelding units are needed in the department?" To answer these questions one must resort to personal opinion. Most educators would agree that personal Opinion varies so widely that its use in this situation is acceptable only because there are no better means avail- able for estimating the time the equipment would be used for giving instruction and for practice. The fact that personal Opinion varies widely was established by Schafer,2 who used the Opinions of nine teachers of vocational agri— culture to assist him in the develOpment of selected units to be taught in farm mechanics. These teachers were in agreement on the content of the units but there were wide variations in opinions as IEducational Objectives in Vocational Agriculture, U. S. Office of Education, Vocational Division.Monograph No. 21, Revised 1955, p. 3. 2Wallace A Schafer, "Teaching Units in.Farm Mechanics for Courses of Study in Arizona.Departments of Vocational Agriculture," (unpub- lished Master's thesis, University of Arizona, Tucson, 1951), p. 2h. S to the time needed for teaching each unit. Their estimates of the time needed to teach the unit on arc welding ranged from.3.25 hours to fiftybfour hours. A wide variation of estimates which dealt with the time needed to teach areas in farm.mechanics was also exhibited in a survey made by Young.3 This was a survey of the instruction offered in farn.mechanics by forty teachers of vocational agriculture in Illinois. It showed that from one to sixty hours were used by different teachers to teach the area of cold metal work. Variations in teaching time for some other areas were almost as wide. The rising cost of equipment needed in farm.mechanics instruction has increased the concern of administrators regarding the number of students who can be expected to develop the skills needed to operate each piece of equipment during a school term. In recent years, there has been a trend toward depending less upon hunches and Opinions and more upon results of research when making decisions that will affect the development and training of students. To decide on the number of arc welding units to install in a school shOp a school administrator needs results of research. There is a need for an estimate, based on research findings, of the time required by students for practice in order to develop the basic Skills in arc welding. There is also a great need for a method r 3Orville L. Young, "What Are They Teaching in Farm.Mechanics?” £gricultural.Education Magazine, 232208, March, 1951. 6. of determining the time that must be allocated to students for practice to develOp the basic skills in other farm mechanics activities. It is believed that this study should make available to teachers of voca- tional agriculture and to administrators information that can be used to (1) increase their efficiency in planning schedules for arc welding instruction, and (2) determine more adequately the amount Of equipment needed to teach arc welding effectively to farm mechanics classes. Also, the method employed in making this study may be used as a guide for individuals who may wish to find the amount of time required for practice by students to develop skills in other farm.mechanic activi- ti-e 8 e §2222.2£.E§2.E§2313 The nature of the study made it necessary that the teachers who cooperated in it be limited to those who had proved that they possessed abilities to teach arc welding in a manner acceptable to authorities in vocational education. The decision to make this limitation was based on the belief that a teacher must know how to perform.the arc welding jObs that he is to demonstrate to a class in farm mechanics. Nineteen supervisors of vocational agriculture in five states and one teacher trainer sent to the writer the names and addresses of one hundred two teachers who had demonstrated to them that they were qualified to teach arc welding. The names of twelve additional teachers were received from supervisors too late to be used in this study. 7 Forty-three teachers participated in the study and returned forms for one hundred twenty-nine trainees during the spring of 1953. During the fall of the following school term.five of the teachers in Virginia who had participated in the study during the spring of 1953 selected sixty-six additional students of vocational agriculture, and each of them practiced until they had deveIOped each of the four skills. Therefore, a total of one hundred ninety-five students of vocational agriculture participated in the study. Iindtations 2f the study. This study has certain limitations inherent in its pattern. The data were secured under circumstances that prevail in regular farm.mechanics classes. An inherent purpose of the study was to secure results that could be used to advance and improve instruction in farm mechanics. Therefore, it seemed logical that farm.mechanics classes would provide the best source from which data could.be secured for the study. many departments of vocational agriculture have only one are welder. This situation put a limitation upon the number of trainees who could practice in a department without interfering with the regular farm.mechanics class schedules. . The number of skills in arc welding to be deveIOped by students of vocational agriculture in this study was limited to four, namely; making a bead, making a fillet weld, making a butt weld, and making a filletdweld lap joint. These skills were to be performed in the flat position. It was not feasible for the writer to examine each of the eight specimen welds accepted from each of the one hundred ninety-five students by the teachers. The writer did, however, observe at least one demonstration by 11.6 per cent of the teachers. He also examined specimen welds prepared by the students and accepted by these teachers. This study did not attempt to support any particular sequence as the most desirable for students to employ in the development of the four basic skills in arc welding. . The study dealt mainly with the time that the trainees devoted to practice before attaining a degree of competenqy that the teachers would accept in light of the criteria set up in the instrument. It was not the purpose of the study,to evaluate the quality of teaching demonstrated by those who participated. Even though these limitations exist, the writer believes that if the findings of this study are properly interpreted and used by teachers and administrators, a contribution will have been made to vocational education and to research. Basic assumptions. In order that this study might progress, the following basic assumptions were necessary. It was assumed; I. That each of the supervisors of vocational education in agriculture and the teacher trainer who cooperated in the study was capable of choosing teachers of vocational agri- culture who had demonstrated their abilities to teach arc welding. 2. That the teachers who cooperated in the study would teach the four basic jobs in arc welding in a manner that was satisfactory to authorities in vocational education in agriculture. 3. That the trainees who participated in the study were representative of the students in vocational agriculture who had not developed the basic skills in arc welding. 1;. That the normative-survey procedure and the use of a data-collecting instrument were reliable methods of securing the data used in the study. 5. That the teachers followed the instructions with regard to demonstrating the Jobs and reporting the time utilized by the trainees in developing abilities to perform the skills . Definition of Terms Farm mohanics. Those unspecialized activities of a mechanical nature that are taught in vocational agriculture and done on the farm with the kinds of tools and equipment that the farmer has accessible. Farm mechanics activities. This term refers to a broad field of training in the vocational agriculture program and includes such areas as the following: Farm Shop Work. Selection, sharpening, care and correct use of shop tools and equipment; woodwork and simple carpentry; sheet metal work; elementary forge work; electric arc and oxyacetylene welding; pipe fitting; simple plumbing repairs; rope work. Farm Power and Machinery. Selection, management, adjustment, operation, maintenance, and repairing (excluding major repairs requiring specialized equipment and services) of farm gas engines, trac- tors, trucks, and the principal farm.machines. Farm Building and Conveniences. Elementary scale drawing and plan reading; farmstead layout; func- tional requirements of farm houses, shelters, and storages, water systems; septic tanks and sewage disposal; heating. Soil and water Management. Elementary leveling, land measurement and farm.mapping; farm.drainage; farm.irrigation; terracing, contour farming, strip cropping. (Emphasis on various phases to be varied in accordance with local or regional needs.) Rural Electrification. Utilization of electricity in the home and in productive farm.enterprises; selection, installation, Operation, and maintenance of electrical equipment. ££g_welding. This term refers to a localized progressive melting and flowing together of adjacent edges of metal by means of heat that is produced and sustained by an electric are between a metallic rod, called an electrode, and the base metal. Electrode. The metallic rod which conducts current from the electrode holder through the arc to the base metal. The tip end of the electrode melts in the heat of the arc and the molten portion is carried across the arc and deposited in or on the base metal. All 1‘Report of the Subcommittee on Agricultural Teacher-Training, Committee on Curriculums (College Division), American Society of Agricultural Engineering, in Collaboration with an Advisory Group of Agricultural Education Specialists, submitted June 22, l9hh. 11 electrodes used in this investigation are coated. This means that the metal rod is covered with a substance which stabilizes the arc and improves the fusion of the metals. £52. The flow of current across a narrow gap between the electrode and the base metal producing heat and a brilliant light or Sparks. Bead. A longitudinal deposit of weld metal from an electrode. Igunngarmer class. A group Of young men, usually between the ages of sixteen and twenty-five years, who are not enrolled in any other school, who are in the process of becoming established in farming, and who are receiving systematic instruction in vocational agriculture. ggb_breakdown. An outline of the steps and key points organized in.the sequence that they should be performed while doing a specific job, used in the same sense as job operation. Step. A logical part of an operation when something is done or happens to make the jOb more nearly complete.5 ggy.pgin . Anything in a step that might make or break the jOb, avoid injury to the trainee or make the jOb easier to perform.6 5Obed L. Snowden, Glen C. Cook and Clyde walker, Practical Rethods ip_Teaching Farm Mechanics (Danville, Illinois: The Interstate, 1955): P0 313' 6222- ai- £22. For the purpose of this study, the term refers to a task to be performed in an orderly manner to develop skill. Skill. This term refers to the ability to perform a mechanical activity with accurady, ease and precision. Practice-time. This term refers to the actual time in minutes that the trainee worked on the job before producing a specimen weld that met the criteria set up in the instrument and was satisfactory to his instructor. Trainees without knowledge 2; arc welding. This term refers to trainees who have never done any arc welding and do not know how it should be done. Trainees with knowledge 25 arc welding. This term refers to trainees who have seen someone do or demonstrate arc welding and trainees who have helped someone do arc welding. Plan of Organization In the chapters that follow a concise report of the study is presented. In Chapter II a review of the literature which has implications for the study is presented. Chapter III is devoted to the design and the methodology used in the study. It contains a description of the techniques used in con- structing the instrument, the method used in selecting the individuals 13 who participated in the study, and of the procedures used in acquiring and analyzing the data. In Chapter IV the data are presented, analyzed and interpreted. The presentation deals specifically with the time required by the students to develop the four skills in arc welding used in the inves- tigation. The analyses and interpretations of the data are related to age, previous knowledge of arc welding, length of time devoted to the demonstrations by the teachers, and lapse of time between the demonstration and the beginning of the practice-time, as they are associated with the time required to develop the four skills. Included in Chapter V are the summary and conclusions. CHAPTER II REVIEN OF RELATED LITERATURE In surveying literature pertaining to time and practice in the deve10pment of abilities to perform.arc welding Jobs, the investiga- tor found.very little research that had been done in this area. not any research on the time required by students to learn welding of any type was found. There were, however, some research findings that were of great value to the investigator in deve10ping the instrument used in the study. Also, some literature was found that helped in formulating a method for conducting the study. Although in some of the publications from which information was secured, scientific methods of investigation were not employed, this information was so closely related to parts of the study that it is included in this chapter. I ll discussion of the literature reviewed will be classified under three headings. l. Instrument for gathering data. 2. Skills and their development. 3. Time used for learning how to weld. Instrument for Gathering Data One purpose of the instrument used in the study was to provide directions for the teachers and the trainees. Also, part of the instrument was a criterion for use in determining when the ability to 15 perform the skills had been attained. One purpose of the study was to determine the time that a selected group of trainees needed for practice to develop the abilities to perfornrcertain‘basic skills in arc welding. The writer used the normative-survey method of research as described by Good, Barr and Scates1 because it seemed to be the method best adapted tolthis study. Che goal of vocational education is the development of manipula- tive skills. Most authorities are in agreement that practice is essential if an individual is to develop skill in an activity. Crawford? is also in agreement with this idea. He is of the opinion that performance is one of the best learning devices. He advises first finding what constitutes good form.in a task and then adopting it. It is only logical to expect a higher degree of efficiency to result from continual practice of the act. He is also of the Opinion that speed should be acquired as well as accuraqy, although in the beginning it is well to sacrifice Speed in favor of accurady. After that process, skill may be improved by repetition. ‘With this thought in.mind the writer proceeded withrthe preparation of the instrument used in the study. The writer followed the suggestions given by Snowden, Cook and 1Carter V. Good, A.‘S. Barr and Douglas E. Scates, Methodolggz ggyEducational Research (New York: Appleton-Centuny-Crofts, Incor- poratea, EH17, p. 286'. eclaude C. Crawford, The Technique gf Study (New York: Houghton mil-in comm, 1928), P0 3520 16 Walker who made this statement: In getting ready to teach skilled jdbs the teacher must be sufficiently prepared to know how to per- form each step correctly in demonstrating the Jab. He should do the following: 1. Hake a job break- down of each skill to be taught. . . . . Each of the jobs used in this study is a manipulative job, therefore, teachers who had exhibited skills in arc welding had to be used in teaching them. As a guide for the teachers, the author pre- pared a job breakdown for each of the skills used in the study. He followed the same pattern in preparing these breakdowns that Kuglerh used for seventeen welding operations in his book, Arc welding Lessons. PhippsS also recommends the use of a job breakdown for teaching manipulative skills. The pattern followed was that of having steps for each operation in the skill listed on the left half of the page and key points for the operations listed on the right half of the page. The number of trainees that would be permitted to work in the welding booth was another factor that had to be considered while developing the instrument. In an attempt to get the maximum use of 3Cbed L. Snowden, G. C. Cook, and Clyde‘walker, Practical Methods in Teaching Farm Mechanics (Danville, Illinois: The Inter- state Printers and Publishers, 1932), p. 161. hHarold L. Kugler, Arc Welding_Lessons for School and Farm.Shop (Cleveland: The James F. Lincoln Ire welding Foundatibn, 195 5. S A Lloyd J. Phipps and Glen 0. Cook, A Handbook on Teaching Vocational grimlture (Danville, Illinois: The Interstate Printers andgiublishers, 19527: p. 161. 17 the welding booth and welding facilities, some instructors permit two or more students to use them at the same time. Slater6 suggests that only one student be permitted to work in an arc welding booth so that he will have maximum use. of both time and equipment. This will also prevent them from learning undesirable habits from one another. Jefferson and Wood had this to say about welding, The most important property, insofar as welding is concerned, is strength. The success of a welded joint is based on how it compares in strength with the “parent metal," that is the material that is being welded. If the joint is as strong or stronger than the parent metal, then the joint is considered a success. The above statement influenced the writer in his development of the instrument. The true test of whether a trainee has developed the skill to make a welded joint is his ability consistently to make that type of joint that would withstand certain tests. Austin tells of three such tests. He says, ”There are three general types of weld tests: nondestructive, partially destructive, and destructive. . . . Destructive tests involve testing the weld to failure in order to determine its quality."8 63. J. Slater, “Training Aims at Basic Skills," Welding Journal, 19:637, September, 191m. 7‘meodore Brewster Jefferson and Gorham Woods, Metals and 593 to Weld Them (Cleveland: The James F. Lincoln Arc Welding Foundation, EEK—p711 8John Benjamin Austin, Electric Arc Welding (Chicago: American Technical Society, 1952), p. 1‘35. 18 Regarding tests to make on welded joints, Austin states, Physical tests give an accurate measure of the true quality of the weld metal, and for this reason they are used more than any other tests for purposes of research, procedure control, and Operator qualifications. . . . Destructive tests are very helpful to the operator, when made in con- junction with any training or test program, because they enable the operator to establish his welding procedure on the basis of the weld metal quality. When these factors have been established, the Operator will have no further difficulty in ad- hering to a high standard of workmanship.9 The purpose of two tests that were used in the study are discussed by'kustin. He says, "The free bend test is designed to show the ductility and general quality of'a butt welded joint.“10 Regarding the other test he states, "The fillet weld break test provides a quick check on the quality of a single Tefilled joint. The operator can readily judge the density of the weld and the degree of fusion to both plates."11 . Another test for welds may be thought of as the appearance test. "A good weld looks good." Combined with good judgment in welding this can be used as a criterion in determining if a weld is good or not. In connection with testing welds Fuller states, in part, The best test for welds is to watch carefully while you are welding. . . . After a weld has been com» pleted you can learn something about it by studying the appearance. Of course this does not mean that Saustin, pp;_cit., 2h5. loIbid., 25h. 11Ibid., p. 256. 19 you can tell the quality of the weld by its appearance alone. Smooth, even ripples are a good indication that you had the weld metal under control. The correct contour of the weld-- a gentle sIOpe from.the center of the edge-~15 good evidence that the weld is sound.12 Some additional information regarding testing welds that related to this study was found in the Procedure Handbook 2; 553 lkgging in the statement that follows: In the early days of welding there was great fear that the welded joints were not going to be strong and that they would not meet the service require- ments for which they were designed. Thus elaborate tests were set up to analyze both the joint and the weld metal itself. In the past fifteen.years the high physical properties of weld metal deposited in the normal way and the amazingly successful performance of welded joints and welded structures of all types has resulted in arc welding being used in most cases without test- ing of the weld metal and joints in any way.13 To produce successful welds consistently one must use elec- trodes that are of good quality and of the proper grade. This is another factor that had to be considered in the preparation of the instrument. Concerning the selection of welding electrodes Mbrford stated, "Since a large part of the metal of farm.maChines and equip- ment is low or medium carbon steel, a good class E-6013 electrode will be found adequate for all general purpose welding.'1h —'—Ir—"" R. L. Fuller, ”How Good Are Your‘welds?" The Welding Journal, 29:77h, September, 1950. 13Procedure Handbook of Arc welding Desi n and Practice, (Cleveland: The Lincolfi Electric Company, l9g5), p. 97h. th. J. Mbrford, Farm Arc weld (Cleveland: The James F. Iincoln L c welding Foundation, 19 , p. 16. 20 The American welding Society has developed specifications for electrodes and filler metals to cover the welding of carbon steels and most of the other metals. The following statement comes from the standard specifications for the electrodes which the writer selected for use in the study. The 3-6013 classification of electrode, although very similar to the E-6012, possesses some worth- while differences. Slag removal is somewhat better and the arc can be established and main- tained more readily, particularly in the case of the small diameters (1/16, 5/6u, and 3/32 inch) thus permitting satisfactory operation with lower open-circuit‘voltage. . . . materials are incorporated in the coating which permits the establishment and maintenance of an arc with alternating current at low currents and low Open circuit voltages. The class E-6013 electrode is designed for welding in all posi- tions. ‘Welds made with this electrode have a minimum.of spatter, a minimumrtendency to undercut, and the beads tend to be fine rippled when properly made. In light of these facts the writer selected this electrode to be used in the study. A large portion of the metal used in the construction of farm machines and equipment is made of low or medium carbon steel; there- fore, this kind of metal was selected to be used in the welding practice by the trainees. Austin has this to say about welding low carbon or mild steel. Practically all low carbon steels offer little difficulty in welding. Those steels that come 6515Procedure Handbook 9; Arc Welding Design and Practice, 92. 933., p. . 21 under low carbon or mild steel classification, are those steels which have carbon below 0.03 per cent. . . . Steels of this type are not hardened appreciably when they are heated to a high temperature and then rapidly cooled, as occurs in the arc welding processes. Further- more the welds are not subject to cracking, and the structure (the parent metal) is not impaired by the welding heat.16 Skills and Their Development It is an accepted belief among most educators that individuals learn quicker when they are interested in the matter that is to be learned. Concerning the teaching of arc welding to students in farm mechanics, Hollenberg says, “Fortunately, arousing interest in arc welding is seldom a problem. The majority of students in farm mechanics have a natural interest in this process which is a relative newcomer to the farm.field.'17 In 1951 Douganla made a study to determine the farm mechanics skills needed and acquired by beginning teachers of vocational agri- culture in Ohio. The welding skills needed to teach farm shop were lgAustin, op. 233,, p. 239. 17Alvin H. Hollenberg, fig! :3 Teach Arc weldingin Farm Mechanics (Cleveland: The James F. Lincoln Arc welding Foundation, ,p.h3. 18 Riley Shelton Dougan, "Farm.Shop Skills and Abilities Needed and Acquired by Beginning Teachers of Vocational Agriculture in Ohio," (unpublished Master's thesis, Ohio State University, Columbus, 1951), p. 1390 22 ranked in order of importance for beginning teachers. The ranks that 'Dougan gave the skills were based upon ratings by thirty-four experienced teachers of vocational agriculture in Ohio. The possible ratings were 'very important,“ "important," "average importance,“‘ Ilittle importance,“ and “no importance." The skill of making a lap weld was rated "important" or higher by'sixtyaone per cent of the teachers; making a fillet weld was rated "important" or higher by eighty per cent of the teachers; and making a butt weld was rated "important" or higher by eighty-two per cent of the teachers. The three skills named in the above paragraph are generally thought of as being basic skills for welding regardless of the posi- tion of the metal. The factor of "readiness" should certainly be given consideration in a study of this nature. Albrecht says this about "readiness" with regards to the develOpment and application of skills in farm mechanics: 0 . . let us not assume that all farm mechanics skills can be developed in a year or two. . . . we have all probably heard about reading readiness-- the point at which the student is able to assimilate and understand what he is able to read. How about manipulative skills readiness-the point at which ~ the student is able to understand what he should do and is physically able to do what he understands should be done. ‘What use is there in trying to help a boy to develop skill in forge work when he is physically incapable of swinging the heavy hammer with one hand while holding the tongs with the other?” 7?? Carl F. Albrecht, "Development and Application of Farm Mechanic Skills and Judgments," Agricultural Education Magazine, 25:68, September, 1952. 23 ‘When skills as complicated as the welding jobs used in this study are concerned, little if any improvement is expected to occur in the absence of practice. would older boys in vocational agriculture learn such skills more readily than younger ones? One might expect an affirmative answer for two reasons: First, it seems reasonable to suppose that the older students, having sensory, neural, and muscular systems of greater maturity, should profit more from.given amounts of practice than the younger students. In the second place, the older students have usually had wider experiences upon which to draw in acquiring new skills and this might be expected to give them.an advan- tage over the younger students. The writings of several authors in the field of child development were reviewed to secure additional background information on this particular phase of the study. The development and application of a manipulative skill.are referred to by Huggett and Millard in the statement, Beginning to write, on the part of the young child, brings into play the musclature of much of his whole skeletal organization. It is not unusual to see a young child attempt his handwriting lesson with tongue in cheek or projecting out of his mouth, along with a tensing of arm.and leg muscles as well. As the response becomes automatic, less muscular cooperation is demanded. In this study arc welding required coordination of movements and control of movements in a horizontal direction and vertical direction 20Albert J. Huggett and Cecil V. Millard, Growth and.learnin in The Elementagy School (Boston: D. C. Heath and Company, 1955), p. 398. 2h at the same time. After the weld has been started the electrode must be moved in a horizontal direction at a relatively slow but uniform. speed to melt the parent metal and deposit molten metal from.the ' electrode along the joint. At the same time, the end of the electrode must be lowered uniformly to compensate for the metal that has been deposited and must become a part of the weld. A uniform.distance between the lower end of the electrode and the parent metal must be held in order that the arc will be maintained. A hand-eye coordina- tion is necessary to control these movements. According to Millard21 a certain degree of maturation must have been attained before certain controlled coordination and performance should be expected of an individual. This author states that, Physical size and proportion are essential in the framework through which motor ability is to function. Organic capacities limit the potentiality of per- formance, and psychological factors provide motivation and direction. In referring to learning of sensorimotor skills as a function of age, Munn has this to say; . . . if the learning of such motor skills improves with age, the results of studies fail to show clear evidence of it. Although children of increasing age usually evidence an increasingly high initial level of performance, which may be accounted for on the basis of greater maturity, greater experience, or both. The gross amount and percentage of improvement Cecil V. Millard, Child Growth and.Development in The Elementary School Years (Boston: D. Ct—Heath and Company:"1951), p. e 221bid., p. 100. 25 resulting from.given amounts of practice do not ap- pear to ghange in any consistent way as a function of age.2 ‘ Time Used for Learning How to weld In only one case did the writer find any literature on research that had been done to determine the amount of time needed for individuals to develop skills in arc welding. The literature examined that gave information on welding schools indicated that one standard practice of the schools is to provide a certain number of hours or weeks of instruction for a course. After completion of the course one is supposed to be able to perform the operations set up in the aims and objectives of the course. Burt2h discussed a lOOO-hour training program for welders that was Operated at Santa Monica Technical School. Upon completion of the course the students are expected to be able to weld in the four positions-flat, vertical, horizontal, and overhead-on the five basic types of joints--butt, tee, lap, corner, and edge-on ferrous and noanerro s metals. The students are also expected to be able to do pipe welding, repair welding and hard-facing. Burt also tells of a specialized sixaweek course in which the Southern Counties Gas Company in California trains its welders. The 23Norman L. Munn, "Learning in Children," Manual 2f Child cholo (Edited by Leonard Carmichael, New York: John Wiley and ODS, 19 g p. 3890 2"‘Fred M; Burt, “Gas Company Trains Its Own welders,“ welding Engineer, 36:h0, June, 1951. 26 author makes the following statement regarding this course: Before applicants are accepted for the schooling, the personnel department gives them a preliminary test to determine aptitudes for this type of work. The test is to show up adaptability rather than developed skill. The percentage of men eliminated is not large. . . . In this Specialized course, little attention is paid to the study of theory. The objective is to impart a good competence in arc and oxyacetylene pipe welding.2 In his textbook, Chaffee26 gives forty-one exercises that are used at the Hobart Trade School in the arcawelding courses. These exercises are designed to help in developing the abilities of the students to do certain arc welding operations. The "average practice" time is given at the beginning of each exercise. The ”average practice” time ranges from.one hour for the exercise, cutting with coated electrodes, to eighteen hours for the exercise, making straight beads in the vertical position. For the three exercises--starting the arc, laying long beads, and controlling the width of beads-a total of fourteen hours is listed as the "average practice" time. All of these exercises are performed on work in the flat position. The average practice time is three hours for the exercise lap joints in the flat position; two hours for the exercise butt joints in the flat position; and two hours for the exercise corner welds in the flat position. _‘ 258m, 22. 33.30, 368,400 , 26Wilbur Johnson Chaffee, Practical Arc welding (Troy, Ohio: Hebart Trade School, Incorporated, 19h2), p. 516. 27 The most outstanding piece of literature related to this study is an article that appeared in a bi-monthly issue of a publication by the Chicago Bridge and Iron Company. The author, Horton, makes this statement: During the past few months many of the girls and young men from the office have been making welds for us. Not one of them had ever done so before-- few had only the vaguest idea of what a weld might even be. Some fortyefive minutes of practice and instruction was given, only sufficient to make it possible for them to complete their task. They all made a butt weld of a fi-inch plate, 8 inches long. These welds were rediOgrnphed,--many showing poor fusion, slag inclusions, gas pockets, and some undercutting. Up to the present we have com- pleted tests on 52 of these welds to find that in tension 17 broke outside of the weld, 16 more showed practically the same strength as the parent metal, and of the remaining 19, only four were below 50,000 lbs. per sq. in. (the lowest being at h3,ooo lbs. per sq. in.). Nick breaks and bend tests were comparatively as good.27 with respect to the time to be used in teaching arc welding to allpday students of vocational agriculture Hollenberg says: Welding skills can be mastered in a relatively short time. If time is available only to teach the basic welding skills, the shorter teaching period oflJunior and Senior years should be used rather than stretch- ing a basic course over four years. Relative to the time needed to learn welding, Phipps makes the following statement: 27Ceorge T. Horton, ”How Good Is a Poor Weld?” 2h§,!gtgz,22:gz, 26:2, January 19h0. 28Hollenberg, m. cit” 13. 1+3 28 Only a relatively short time is required to train a farmer to do the welding he needs to do on a farm. Complex welding jobs on a farm, of course, should be done by an expert.29 Summary No literature was found that dealt with research to determine the time required by students to learn any type of welding. The related literature reviewed for this study points toward facts in three main categories. The first category is on the point of developing skill. Edu- cators seem.to be in agreement that for an individual to develop skill in performing a manipulative operation he must learn what to do and how to do it properly, then he must practice. ‘When manipulative Operations are broken down into simple steps, learning them is made less difficult. The job breakdown is recommended by several of the leading farm.mechanics authors to attain this objec- tive. Tests can.be used to pinpoint the need for additional instruction in a specific area and they may be used to determine how successful one has been in the acquisition of a skill. The writers who prepared literature that dealt with the testing of' welds were in agreement on the fact that joints should always be strong and well fused. The manner of testing weld joints to ascertain their .____§_________. 9quyd J. Phipps, et al., Farm Mechanics Text and Handbook (Danzille, Illinois: The Interstate Printers and Publishers, 195h), p. 2 3. 29 strength and degree of fusion may vary since there are several reliable tests. One author believes that the best time to begin examining a weld is while it is being made. Several authors believe that during a training course, the inside of completed welded Joints made by trainees should be examined. In other words, the welded Joints should be given destructive tests. This will enable one to determine the faults and corrections that should be made. One can learn much about a weld from its outside appearance. A.we1ding electrode, 3-6013, that will weld low carbon or mild steel was recommended in the literature for general use in farm mechanics because much of the farm machinery and farm equipment are fabricated from metals of this class. Several authors provided evidence that the maturity and the degree of development of an individual should be considered when instruction is given to develop manipulative skills. The third category is on the matter of time needed for learning how to weld. According to the literature,farmers and members of all-day classes in vocational agriculture can learn to do arc welding. The attempts to learn how well one can weld after having a little instruction and practice provided evidence that the ability to do arc welding can be deveIOped within a reasonable length of time. CHAPTER III METHOD OF INVESTIGATION The particular type of normative-survey procedure employed in the study consisted of using a data-collecting instrument, analyzing the data, making interpretations of the data, summarization of the data, and drawing conclusions. An explanation is given in this chapter of how the instrument was prepared and used in collecting data for the study. Explanations of the methods used in analyzing the data are also given. Preliminary Activities One of the first steps in the investigation was to develop criteria which were used as a guide in selecting preliminary farm mechanics jobs for the study. After the criteria were developed, twelve Jabs in the area of farm.mechanics were selected for pre- liminary evaluation. After evaluating the jobs, the chairman and members of the author's guidance committee approved the use of four jdbs in arc welding. The author made an exhaustive search for literature dealing with the time required to deve10p farm mechanics skills before at- tempting to construct the instrument. The kinds of literature reviewed included unpublished theses, periodicals, bulletins, textbooks, pamphlets and leaflets. Letters were written to several manufacturing companies that have carried on time and motion studies 31 .in connection with the production of their commodities. It was found that a few studies had been made of certain phases of vocational agriculture in which the time used to develop skills in farm mechanics activities were expressed as opinions of teachers. Actually, very little information was found that applied specifically to the devel- Opment of any type of mechanical skills. Some results of research on learning that have implications for this study are reported in the review of literature. The author did not find any methods that had been tested that would be used as a guide for1mmking the study. In view of this it seems highly prdbable that the procedure develOped and used in this study might well provide a method by which the time required to develop other skills in farm.mechanics might be studied. It was apparent that a data-collecting instrument had to be prepared and used to solve the problem of this study, therefore, the next step was that of preparing the instrument. Preparation of the Instrument The instrument1 developed is largely a teaching device which consists of the following parts: (1) instructions to the teacher on the use of the instrument, (2) a job breakdown fer use in demonstra- ting sach of the four skills in arc welding, (3) a sheet for use in classifying the trainees and recording the time devoted to practice, and (h) a sheet of instructions for the trainees to use after making igee Appendix A. 32 a bead with the arc welder. Instructions tg_the teacher. The author recognized the fact that the instructors would not have identical teaching facilities and equipment. Also it was imprdbable that all the instructors would teach the same job in exactly the same manner. Therefore, by pro- viding them with a set of instructions it was thought that a more nearly uniform procedure might be followed in giving the demonStration, recording the results and reporting the results. JOb breakdown. After reviewing literature related to the four basic skills in arc welding a job breakdown was prepared for each skill. The job breakdowns follow very much the same pattern as the Operation'breakdowns used.by Kugler2 in his welding operation eXercises. This plan was used because it is one of the most effec- tive methods for teaching manipulative jobs. It contains the steps needed for the demonstration, and it can serve as a guide for the trainee while practicing to develop each of the skills. A jdb breakdown was prepared for each of the jObs and they were arranged in the instrument in the following order: Nb. 1. Striking an arc and running a bead. No. 2. making a fillet weld. No. 3. Making a butt weld. 2Harold L. Kugler, Arc welding Lessons for School and Farm Sh (Cleveland: The James F. Iincoln Arc welding Foundation, 1§§0). pp- 129-308. 33 No. 14. Making a fillet-weld lap joint. Classification of trainees and record 21... time. It was decided in the early stages of the study that members of vocational agricul- ture classes would be used as trainees. The situation in which the trainees practice to develop the skills will be the natural setting of a farm mechanics class. To secure a more nearly accurate measure of the time used by the trainees to develop each skill, it was deci- ded that individuals would be selected who were without experience in arc welding and if the individuals had knowledge of arc welding, that knowledge was indicated by placing a mark before the second or third statement in Part 1.3 The form that was developed to be used in selecting and classifying the trainees had features somewhat similar to the device prepared by Claninh for determining the farm-job experiences of students of vocational agriculture. The form that was used in this study contained three classifications. The classifica- tions were based upon the trainees' experience and knowledge of arc welding. The form on which the amount of practice-time was recorded constituted another part of the instrument.5 On this form spaces 38% Appendix A, Form 1, Part I. ”Edgar Clanin, "The Developmnt of 1 Device for Determining the Farm-Job Experiences of Students of Vocational Agriculture," (unpub- lished Doctor's dissertation, Purdue University, West Lafayette, Indiana, 1951), 133 pp. 5See Appendix A, Form 1, Part II. 314 ‘were provided for answers to four specific questions for each of the four skills. The first three questions were directed to the trainee. The fourth question was to be answered by the teacher. The questions were as follows: 1. Did you begin practicing immediately after the demonstration? One of the two possible answers, "yes" or "no," was to be checked in the space provided under the skill. 2. If the answer to item.l is "no,” how long was it before you did begin practicing? The answer was limited to a number of days or hours and it was to be written in the space under the Skill. 3. How much time did.you spend practicing before doing the job twice successfully? The answer to this question was limited to minutes and it was to be written in the space provided below each skill. h. How much time was used to demonstrate the 30b? The answers were limited to minutes. Space was provided under each skill for the teacher to record the time. An effort was put forth to make it convenient and easy for the instructors and trainees who participated in the study to record and return the data. The parts of the instrument that dealt with classi- fication of the trainees and record of time were on one sheet and identified as Form 1. A separate Form 1 was provided each trainee who participated in the study. The teachers were given directions in the instructions for returning the forms to the investigator. 35 Instructions for trainees. The teachers were asked to give the instructions and directions in their usual manner of teaching while demonstrating the arc welding jobs. The author constructed Form 2, for two purposes; (1) to assist the trainees in diagnosing the troubles that might cause the more common types of poor beads and poor welds and, (2) to help the trainees decide when a good bead and a good weld had been produced. To assist in the accomplishment of these purposes directions were provided at the top of the page. Im- mediately below the directions a photograph, 1} inches by'2 inches, of each commonly made type of head was Shown on the right side of the page. To the left of each photograph there was a verbal description of four characteristics of that particular type of bead. A photo- graph of a good bead was located at the top of the page and below it five of the most common poor beads were located. By following the directions, the trainee compared the bead he had made with the photographs and the written characteristics on Form 2. This consti- tuted the surface appearance test which was a part of the inspection given to each weld. Pilot studies of the instrument. The first draft of the instrument was prepared and a member of the staff in the Agricultural Engineering Department at Michigan State University used it with a selected group of students in a farm.mechanics Short course. He analyzed it in a critical manner and offered suggestions for its improvement. The second draft was prepared in light of these 36 suggestions. The second draft was duplicated and copies were mailed to four teachers of vocational agriculture in Michigan and to the farm mechanics instructor at'Virginia State College. In all cases a personal letter was sent to the teachers and they were asked to try out the instrument with at least two of their students and to offer suggestions for its improvement. Three teachers cooperated in this pilot study. The suggestions given by these teachers resulted in several changes in the instrument. A critical evaluation and analysis of the instrument by the chairman and each member of the guidance committee resulted in further changes. In its final form, the instrument consisted of seven parts. A complete copy is included in the Appendices. I Collecting the Data Inasmuch as this was a study to determine the practice-time required by students of vocational agriculture to develop basic skills in arc welding, it was decided that the data should be secured from individuals in farmpmechanics classes. Selection.2£ the states. The two main criteria used to select the states in which teachers and students would be asked to partici- pate were (1) that more than ninety per cent of the farms in the state have electrical service, and (2) that the state is located in the Southern Region or the Nerth Central Region as defined by the Division of Vocational Education, United States Office of Education. 37 The states selected were as follows: Illinois, Indiana, North Carolina, Ohio, Michigan and Virginia. Selection g£_the teachers. A personal letter was sent to the District and/or Area Supervisors of Vocational Agriculture in each of the states selected for the study. In this letter they were asked to recommend six teachers who had demonstrated their abilities to do a good job of teaching arc welding. This was requested in order that only teachers who were competent to do the job might be selected. A self-addressed and stamped envelope was included with each letter. Each supervisor responded by recommending at least five teachers. The names and addresses of five teachers in Michigan were given to the author by'a member of the teacher-training staff in Agricultural Education at Michigan State University. ggili£g_the instrument. The instrument of this study was mailed on March 20, 1953, to eighty-nine teachers who had been selected. Four copies of Form 1 were included with each instrument. A letter stating the purpose of the study, giving the reason for including that teacher's name on the selected list and a request for his cooperation was also included with each instrument. A self-addressed, stamped envelope was included to help encourage the participants to return the forms. As the "returns" came in they were tabulated and checked against the original mailing list. A followaup letter was sent to each teacher from whom a reply had not been received by the tenth of May. 38 By May twenty-first, forty-three teachers had returned forms for one hundred twenty-nine trainees. Four teachers in Michigan and two teachers in Ohio sent letters to the writer stating that their classes in vocational agriculture had already completed the instruc- tion in arc welding that had been planned for that school term. Recording the data. The forms that were returned gave the following information for each trainee: (1) name, (2) age in years, (3) indication whether a member of an all-day class or young farmer class, (h) indication of his experience and knowledge of arc welding, (5) when he began practicing after the demonstration was given, (6) the amount of time in minutes devoted to practice before develOping each skill, and (7) the amount of time in minutes the teacher used to give each demonstration. As the “returns" came in the data were recorded on a form that the writer prepared for this purpose. Sggggd‘gampl_. It was felt that the value of this investiga- tion would be enhanced by comparing the results of the performance of a second sample of trainees who used the instrument of this study with the results of the first sample. ‘With this thought in mind the writer selected five teachers of vocational agriculture in Virginia who had participated in the initial part of the study to assist him in securing data for this phase of the investigation. Each of the teachers who were selected worked in a department that was located near enough to the writer so that he could work with the teachers 39 and the trainees personally. The writer visited and observed each teacher give a demonstration to his portion of the sixtyasix trainees who participated in the second sample. The writer observed the trainees inspect their welds and he saw at.least one welded specimen that was prepared by each trainee and accepted by his teacher. The data collected in the second sample were analysed and treated in the same manner as those of the original sample. Appro- priate statistical methods were used to compare the findings of the two samples. The methods used in making the analyses and comparisons are described in the section that follows. Methods Used In Analyzing the Data To help answer the questions asked in the problems of the study the following procedure was used: 1. Hypotheses based on the questions asked in the problems were formulated regarding each skill. A statement of the hypothesis is given at the beginning of each section that pertains to the skills. 2. The hypotheses were tested and accepted or rejected on the basis of the value of the probability that a value as unusual as that of the sample statistic would have been observed from the sampling distribution. 3. The results of the tests were interpreted. It was felt that an explanation should be given of the null ho hypotheses as used in making certain analysis in the study. On the basis supplied by observation of a sample we are not able to say that this or that is absolutely certain or not certain about the universe from which the sample was drawn. Hagood and Price6 point out that by statistical methods we can come nearer to proving that something is not true about a universe than that something is true. In light of this, a negativistic approach is often used in securing information about a statistic. This method is explained in an ap- propriate manner by Hagood and Price in the following statement regarding the null hypothesis: If we want to establish one hypothesis, we shall not test it directly but shall formulate the op- posite hypothesis, which we shall call the null hypothesis, and test it on the basis of the evidence from.our sample. If the evidence is such as to cause us to reject or discard the null hypothesis and if the hypothesis we wanted to establish is the only alternative hypothesis, then the rejection of the null hypothesis is the equiva- lent of the Confirmation of the original hypothesis.7 The above statement served as a basis for the formation of the hypotheses used in the study. The three statistical methods used to secure evidence that would enable the writer to accept or reject the hypotheses set forth in the study were as follows: 6 Margaret Jarman Hagood and Daniel 0. Price, Statistics for Sociologists (New York: Henry Holt and Company, 1952), p. 237. 71bido’ p. 237-8. hl 1. Analysis of variance. 2. The t-test of significance of a difference between the means. 3. Coefficient of correlation. The five per cent level of significance was employed as the' point beyond which an Observed deviation of the statistic from the mean would be considered great enough to be classed as “significant" in this study. The selection of the five per cent level of significance by the writer conforms with the practice recommended by ‘Walker who stated, "Each experimenter may properly set up his own definition of significance, so long as he informs his readers as to what it 13.n3 Analysis 9f variance. It was suggested by Croxton and Cowden9 that analysis of variance is an appropriate method to use when seeking statistical evidence that may be used as a basis for accep- ting or rejecting a hypothesis in which several groups are compared simultaneously. The procedures which follow are for convenient calculation of ’of the sums of squares and degrees of freedom involved in the analysis of variance of N observations, distributed among k groups BHelen Mt‘walker, Elementary Statistical Method§_(New York: Henry Holt and Company, l9h3), p. 292. 9Frederick E. Croxton and Dudley J. Cowden, Applied General Statistics (New'York: Prentice-Hall, Inc., l9h6), p. 351. h2 of ma individuals each. For the purposes of setting forth the compu- tational procedures used in this investigation let 113 be the practice time of the ith group k be the number of groups ”j be the number of individuals in 3th group N be the number of observations in all k groups; i.e., k N . m :17}: t: be the total of the observations of the 3th group T be the total of the observations in all k groups; i.e., k T - EL; t1 2 The total sum.of squares, xT’ may'be calculated from m. 2 2 ‘ lid-#155. are. The groups sum of squares, XE, may be calculated from Z%' tg *i'i*°-°°ii- T2 "*1 "‘2 1m3 “1: N 2 The within-groups sum of squares, x“, may be calculated from 2 2 _ 2 2‘91 '25 “2‘s The number of degrees of freedom.corresponding to the total sum.of squares, d.f.t may be Obtained from 3 h3 def. . k-l T The number of degrees of freedom corresponding to the within groups sum of squares, d.f.W, may be calculated from defow - dofoT - d.f.G The t-test. The t—test of significance was used in.the study whenever the means of two groups were compared. Hagood and Price state, Frequently we are interested in testing the significance of the difference between the nean of one distribution and the mean of the other. To test the significance of the difference be- tween two means, we test the null hypothesis that the two means were observed from samples which may have been drawn from.the same universe. If the probability of observing two means differing as widely as those actually observed is small enough, we reject the hypothesis and declare the difference between the two means to be Significant. o 010 A procedure given by Snedecorll was used throughout the study when testing the significance of the difference between the means of two groups. This procedure of testing was used because the sizes of the various pairs of groups were not equal. 'When the groups are not equal in size, in order to obtain maximum accuracy the population variance of both groups must be weighed by their 10Hagood and Price, pp. 323., p. 31h. llGeorge Snedecor, Statistical Methods (Ames, Iowa: The Iowa College Press, Fourth edition, I§H5), p. 82. respective degrees of freedom. These factors are included in the foranlla given below. 1': ' i 1 n_ V 111112011 * lllz-QT ‘ ( + 112) 512 n1 Where: 3:- I the difference between the group means n1 I the number of trainees in the group that was without knowledge of arc welding n2 I the number of trainees in the group that had knowledge of arc welding 5x2 I the pooled sum of squares of the two groups For this part of the study the test of significance was made by using the Student's t-distribution Table12 and comparing the value of t, as calculated by use of the formula stated above, with the value of t as found in the Table at the five per cent level of significance for one hundred twenty-seven degrees of freedom for the first sample and sixty-four degrees of freedom for the second sample. Coefficient pf Correlation. The writer assigned the letter “K“ to the distribution of values for the practice-time in minutes re- quired by the trainees to develop the ability to perform a skill. The letter "Y‘ was assigned to the distribution of values for the time in minutes used by the teachers to demonstrate a skill. The 12 \ Snedecor, pp. 933., p. 65. next step was to calculate the summation of the X-values for the skill and calculate the summation of the Yavalues for the skill; to calculate the summation of the square of each Xavalue and the square of each‘Yavalue; and to calculate the summation of each XIdvalue. A formula was selected to compute the correlation coefficient that utilized the original summation values of the practice-time required by the trainees and the demonstration time used by the teachers. This formula was given.by Hagood and Price.13 Nm - (2x) (222 '[m2 - (21)”) [m2 - (2272] r I correlation coefficient "3 ll N I number of pairs of variables X I practice-time in minutes used by trainees to develop ability to perform each skill Y I time in minutes used by teachers to demonstrate each skill The final step was to make the F-test of significance. This test was made by calculating the value of F from a.formula and procedure as given by Hagood and Price.”4 The formula is as follows: F- r2(N-2) 1-132 BHagood and Price, 92. 333., p. L13. 1"‘Ibid” p. h31. b6 r2 I value of coefficient correlation squared N I number of pairs of variables (one hundred twenty-nine in the first sample and sixty-six in the second sample). The degrees of freedom for the F-test are one and one hundred twentybseven for the first sample and one and sixty-four in.the second sample, n1 I 1 degree of freedom and n2 I N - 2. By referring to the Table of F,15 which shows the five per cent ‘points for the distribution of F, it was found that a calculated value of F with one and one hundred twenty-seven degrees of freedom must exceed 3.92 to be of significant value at the five per cent level. Therefore, unless the calculated.value of F for the skill is greater than 3.92, the hypothesis pertaining to that skill may be accepted. The formula used to calculate the fiducial limits is as follows: Lower limit I 2'- 1.960'i Upper limit I i + 1.960 1' When: . -X’I the mean 6} I g; I standard error of the mean. VT The data are presented and analyzed in the next chapter. lsHerbert Arkin and Raymond R. Colton, Tables for Statisticians (New York: Barnes and Nbble, Incorporated, 1930): P. 120. CHAPTER IV PRESENTATION AND.ANALYSIS OF DATA The purpose of this chapter is to present and analyze the data used in the study. In this chapter the trainees who participated in the study have been described in terms of their ages, the size of group with.which they practiced to develop the four skills and in terms of the practice-time required to develop the ability to per- form.each of the four basic arc welding skills. The trainees were divided into groups on the basis of (l) the age of the trainees, (2) whether or not the trainees had knowledge of arc welding before participating in the study, and (3) whether or not the trainees I began practicing the day the skill was demonstrated, afterwhich the practice-time required by each of the groups to develop each of the four skills was analyzed. Also, the time used by the teachers to demonstrate the skills was correlated with the practice-time re- quired by the trainees to develop the skills. Distribution of Trainees It is shown in Table I that one hundred twenty-nine trainees and forty-three teachers of vocational agriculture participated in the first sample used in the study. They were from five states, two of which are located in the Southern Region and the other three are located in the North Central Region. Sixtybsix trainees and five teachers participated in the second sample all of whom were h8 located in the State of Virginia. TABLE I TRAINEES AND TEACHERS WHO PARTICIPATED IN'THE.STUDY BY STATES States Number of Number of Trainees Teachers First Sample Virginia 76 25 Ohio 28 10 North Carolina 1).; 1; Illinois 9 3 Michigan 2 1 Total 129 53 Second Sample Virginia 66 5* _I: Grand Total 195 h8 *These teachers also participated in the first sample. Table II shows the number of trainees that each teacher worked with in the study. In the first sample, four teachers worked with one trainee each, six teachers worked with two trainees each, twenty-two teachers worked with three trainees each, eight teachers worked with four trainees each and three teachers worked with five h? trainees each. The mean number of trainees per teacher was 3.0 in the first sample. In the second sample, three teachers worked with twelve trainees each, one teacher worked with fourteen trainees and one teacher worked with sixteen trainees. The mean number of trainees per teacher was 13.2, in the second sample. No teacher demonstrated to more than six trainees at any one time. TABLE II TRAINEES GROUPED IN TERMS OF THE NUMBER TAUGHT BY THE SAME TEACHER Number of trainees Number of teachers Total number 6? in each group who who taught trainees trainees taught were taught by the in group sizes as in groups of the same teacher shown in column (1) sizes shown in column (1) (1) (2) (3) First Sample 1 . h h 2 6 12 3 22 66 l; 8 32 S 3 15 Total 1.3 129 Mean number of trainees per teacher 3.0 Second'Sample .12 3 36 1h 1 1h 16 l 16 Total 5 66 mean number of trainees per teacher 13.2 50 Table III shows the distribution of the trainees by ages in years. The description of performances is presented for groups as a whole, the groups being differentiated on the basis of the age of the trainees. The ages of the trainees ranged from fourteen to thirty-sixzyears. TABLE III AGES OF TRAINEES IN YEARS First sample Second sample Age in Years Frequencies Frequencies 1h It 6 ‘ 15 20 15 16 h? 19 17 32 10 18 and over 16 16 Total 129 66 Grand Tbtal 19S M For this particular description, the trainees will be referred to in terms of age groups hereafter. For example, all trainees who were fourteen years of age will be referred to as the fourteenqyear- old-trainees group. In both samples, the smallest number of trainees was in the fourteenayear-old-trainees group and.the largest number of trainees was in the sixteenqyear-old-trainees group. 0f the 51 trainees in the first sample who were in the eighteeneyear-old-and over-trainees group, twelve were in all-day classes and four were members of young farmer classes. In the second sample, thirteen of the trainees in the eighteeneyear-old-and-over age group were members of young-farmer classes. There were no members of young-farmer classes less than eighteen.years of age in either sample. Almost eightyafour per cent of the trainees were between fourteen and eighteen.years of age. The five age groups will be further described by means of the average practice-time in minutes and measures of variability as required for the development of the ability to perform four basic arc welding skills. It seems Justifiable to exPlain at this point how certain analyses that will follow were made. Observation of differences be- tween or among means naturally raises the question of whether or not the differences are so large that the samples in.which they were computed are from the same normal population. Stated otherwise, whenever differences between or among means are observed the question of whether or not the differences could have arisen as the result of vagaries of sampling from the same normal population naturally comes to mind. If the probability of a difference or several differences in sampling from.the same normal population is small, say five per cent or less, it is reasonable to conclude that the sample means are estimating different population parameters. The procedure for answering the question of whether or not differences are too large to be accounted for by'the sampling variation of statistics is a 52 null hypothesis to the effect that the differences among population means is zero, is stated. Then its creditability is tested by use of an appropriate test criterion. ‘Where two groups are involved Student's t test is utilized. Where more than two groups are in- volved the analysis of variance technique leading to an F test is utilized. The null hypothesis is rejected if the value of F is as large as or larger than the value which.will not be observed more than five per cent of the times in sampling. If it is smaller than such a value the null hypothesis is not rejected. The level of significance adopted for this study is the five per cent level. Hence, the probability of rejecting the null hypothesis when it is true will not exceed five per cent. The analyses of the practice-time required by the trainees to develop the four skills follow. Age of Trainees and Practice-Time flaking _a_ bead. Shown in Table IV are values for the practice- time in minutes required by five age groups to develop skill in making a bead with the arc welder. In the first sample the seventeenqyear-old trainees required the smallest mean practice-time, h8.5 minutes. For this group the standard deviation was 36.3 and the range was ten to one hundred sixty minutes. The fourteenpyear- old trainees had the largest mean practice-time, 5h.9 minutes. The standard deviation for this group was 32.h and the range was eighteen to one hundred twenty minutes. 53 TABIE Iv PRACTICE-TIME IN MINUTES REQUIRED BY FIVE AGE GROUPS TO DEVELOP THE ABILITY TO MAKE.A BEAD WITH THE ARC WELDER fl Groups Number Mean Range SD Fourteenayear-old (1) 1h 59-h 18-120 32.h trainees (2) 6 58.3 25-97 21.6 Fifteenqyear-old (1) 20 52.1 3-183 hh.9 trainees (2) 15 59.3 7-90 22.2 Sixteeneyear-old (l) h? h9ol h-IBO h8.6 trainees (2) l9 hl.8 5-95 27.0 Seventeenqyear-old (l) 32 h8.5 10-160 36.3 trainees (2) 10 36.6 6-89 26.9 Eighteenayear-old- (1) l6 Sh.3 16-180 h1.h and-over trainees (2) 16 50.8 15-120 28.? Note: Rows (1) contain values from the first sample and rows (2) contain values from the second sample. In the second sample, as in the first, the seventeenfiyear-old trainees had the smallest mean practice-time, 36.6 minutes. For this group the standard deviation was 26.9 and the range was six to eighty-nine minutes. The fifteenqyear—old trainees had the largest mean practice-time, 59.3 minutes. The standard deviation for this group was 22.2 and the range was seven to ninety minutes. After observing the differences among the means the question arises as to whether or not the differences among the means of practice-time for the five age groups were statistically significant. Sh To help answer this question it is in order to test the hypothesis that the samples fromuwhich the means of each of the five age groups were calculated were from.the same normal population. For this purpose the analysis of variance technique, leading to the F-test of significance, is appropriate. The null hypothesis tested was stated ‘ as follows: The differences among the means of the practice-time required to develOp the ability to make a bead with the arc welder are in the pOpulation of which the sample is representative equal for the fourteeneyear-old trainees, fifteeneyear-old trainees, sixteen- year-old trainees, seventeeneyear-old trainees, and the eighteenp year-old-and-over trainees. Since the null hypothesis tested for each of the four skills would be stated so much alike, only the first one is stated. It is shown in Table V, which relates to the skill of making a bead, that for the first sample the ratio of the between-group variance to the within-group variance produced .213 as the value of F. Since the value of F is considerably smaller than the value of F which would be Observed in five per cent of all random samples from the same normal population, the null hypothesis was not rejected. In the second sample the ratio of the between-group variance to the within-group variance produced 1.606 as the value of F. Since the value of F is smaller than the value of F which would be observed in five per cent of all random.samples from the same normal population, the null hypothesis is not rejected for the second sample. TABLE V MSIS OF VARIANCE OF PRACTICE-TIME IN MINUTES USED BY TRAINEE IN FIVE AGE GROUPS TO DEVELOP THE ABILITY TO MAKE A BEAD WITH THE ARC WELDER Source of Sum.of Degrees of Mean square Variation Squares Freedom. Variance F First Sample Total 229,032.25 128 Between-group 1,567.95 h 391.98 213* Within-group 227,h6h.3o 121; 1, 83h.39 Second Sample Total h9,05h.667 65 Between-group h,67h.h01 h 1,168.600 105:5 Within-group hh,380.266 61 727.515 A _.__‘.4l *The value of F in the first sample must equal to or exceed 2.hh to be significant at the five per cent level with h and 12h degrees of freedom. *aThe value of F in the second sample must equal to or exceed 2.52 to be significant at the five per cent level with h and 61 degrees of freedom. Makigg_g fillet weld. In Table VI the values for the practice- time in minutes required by five age groups while developing the skill of making a fillet weld with the arc welder are shown. In the first sample the sixteen-year—old trainees had the smallest mean practice-time, hh.h minutes. For this group the standard deviation was h3.9 and the range was five to 170 minutes. The eighteenpyear-old andpover trainees had the largest mean practice-time, 60.3 minutes. 56 For this group the standard deviation was 50.0 and the range was ten and one hundred sixty minutes. TABLE VI PRACTICE-TIME IN MINUTES REQUIRED BY FIVE AGE GROUPS TO DEVELOP THE SKILL MAKING A FILIET'WELD‘WITH THE ARC WELDER J—t .— ”f Groups Number Mean Range SD Fourteeneyear-old (1) lb h6.1 8-lh0 hl.0 trainees (2 ) 6 10.8 hS-Sh 3.1 Fifteenayear-old (l) 20 53.2 h—180 50.h trainees (2) 15 52.8 25-75 1h.9 Sixteeneyear-old (1) h? hh.h 5-170 h3.9 trainees (2) l9 h2.0 15-87 18.0 Seventeenqyear-old (l) 32 h6.9 9-180 h5.5 trainees (2) 10 h6.2 20-90 22.0 Eighteeneyear-old-and (l) 16 60.3 10-160 50.0 over trainees (2) l6 50.h 15-115 22.5 Note: Rows (1) contain values from the first sample and rows (2) contain values from the second sample. In the second sample as in the first the sixteeniyear-old trainees had the smallest mean practice-time, h2.0 minutes. For this group the standard deviation was 18.0 and the range was fifteen to eightybseven minutes. The largest mean practice-time, 52.8 minutes, was in the fifteengyear-old trainees group. The standard deviation and range for this group were 1b.9 and twenty- five to seventy-five minutes, respectively. 57 In Table VI differences are Observed among the means of the age groups for the practice-time required to develop the skill of making a fillet weld with the arc welder. The null hypothesis regarding the skill, making a fillet weld, was formulated and tested. It is shown in Table VII that when the F-test was applied in the first sample, for testing this null hypothesis, the ratio of the between group variance to the within-group variance produced .h30 as the value of F. The value of F is considerably smaller than the value of F which would be Observed in five per cent of all random samples from the same normal population, therefore the null hypothe- sis is not rejected for the first sample. In the second sample the ratio of the between-group variance to the withinpgroup variance produced .673 as the value of F. Since the value of F is smaller than the value of F which would be Observed in five per cent of all random samples from the same normal population, the null hypothesis is not rejected for the second sample. m a but: wild. It is shown in Table VIII that the smallest mean practice-time, 33.h minutes, required by a group in the first sample to develop the ability to make a butt weld with the arc welder was obtained by the fourteen-year-old trainees. For this group the standard deviation and the range for this group was 33.h and fifteen to one hundred thirty minutes, respectively. In the second sample, as in the first, the fourteen-year-old trainees had the smallest mean practice-time, h0.3 minutes. For 58 TABLE VII ' ANAHSIS CF VARIANCE CF PRACTICE-THE IN FELNU'IES USED BY TRAINEES IN FIVE AGE GROUPS TO DEVELOP THE ABILITY TO MAKE A FILLET WELD WITH THE ARC “ELDER Source of Sum.of Degrees of Mean Square _‘Variation Squares Freedom Variance F First Sample Total 263,909.69 128 Betw - on 3 611.85 902.96 een gr p ’ h .h30* Within-group 260,297.8h 12h 2099.18 Second Sample Total 26,812.666 65 Between-group 1,133.138 h 283.28h .673** 'Withinpgroup 25,679.528 61 h20.975 _.A_‘ *The value of F in the first sample must equal to or exceed 2.hh to be significant at the five per cent level with h and 12h degrees of freedom. aaThe value of F in the second sample must equal or exceed 2.52 to be significant at the five per cent level with h and 61 degrees of freedom. this group the standard deviation was 10.7 and the range was twenty-nine and fifty-five minutes. 50.7 minutes, was in the eignteenfiyear-old-and-over trainees group as in the first sample. The standard deviation.and range for this group were 26.6 and fifteen to one hundred five minutes, respectively. TABLE VIII The largest mean Iractice-time, PRACTICE-TIME IN MINUTES REQUIRED BY FIVE AGE GROUPS TO DEVELOP THE SKILL MAKING A BUTT WELD WITH TEE ARC WELDER Groups Number Mean Range SD Fourteen-year-old (1) 11: 33.1: 3-70 16.8 trainees (2) 6 140.3 29-55 10.7 Fifteeneyear-old (l) 20 h0.l 3-150 3h.2 trainees (2) 15 h8.1 32-95 111.9 Sixteeneyear-old (l) h? 37.5 3-170 36.7 trainees (2 ) 19 hi! .3 25-73 lb .2; Seventeenayear—old (l) 32 35.2 10-109 25.6 trainees (2) 10 h6.6 26-68 13.h Eighteen-year-old- (1) l6 h3.2 15-130 33.h and-over trainees (2) 16 50.7 15-105 26.6 W Rows (1) contain values from.the first sample and rows (2) contain values from the second sample. Nets: Do the differences among the means of the five age groups for the skill, making a butt weld, represent differences that should . be expected in a sample of this size if, in fact, the means are from the same normal pOpulation? An answer to this question was found r 60 by using the analysis of variance shown in Table II to test the null hypothesis regarding the skill making a butt weld. When the F-test was applied to the first sample the ratio of the between-group variance to the within-group variance, as shown in Table IX, produced .633 as the value of F. The value of F is considerably smaller than the value of F which would be observed in five per cent of all random samples from the same normal population therefore, the hypothesis is not rejected. TABIE IX ANALYSIS OF VARIANCE OF PRACTICE-TIME IN MINUTES USED BY TRAINEES IN FIVE AGE GROUPS TO DEVELOP THE ABILITY TO MAKE A BU'I'I‘ WEID WITH THE ARC WEIDER w m Source of . Sum of Degrees of Mean Square Variation Sguares Freedom Variance F First Sample Between-group 2 .551; .72 h 63 8 . 68 0633* V11 thin-group 12h , 978 .21 121; 1007 . 89 Se c ond Sample Total 21,887.931 65 Between-group 880 .hh9 14 220.112 .63 994* Within-group 21,007.h82 61 31.1mm; *The value of F must equal to or exceed 2.hb, to be significant at the five per cent level with h and 12).; degrees of freedom. *sThe value of F must equal or exceed 2.52 to be significant at the five per cent level with h and 61 degrees of freedom. 61 Table IX shows for the second sample the analysis of variance of the practice-time in minutes used by sixty-six trainees in five age groups to develop the ability to make a butt weld with the arc ‘welder. It is shown in the table that the ratio of the betweene group variance to the within-group variance produced .639 as the value of F. Since the calculated.value of F does not equal to or exceed the value, 2.52, the value of F, which would be observed in five per cent of all random.samples from the same normal population, the hypothesis as applied to the skill of making a butt weld was not rejected. Egging_a.filletaweld lap joint. Shown in.Table X are the means of the practice-time, in minutes, required by five age groups to develop the skill of making a filletaweld lap joint with the arc welder. In the first sample the fourteen-year-old trainees had the smallest mean practice-time, 26.1 minutes. For this group the standard deviation was 13.6 and the range extended from six to fiftybfour minutes. The seventeenayear-old trainees had the largest mean practice-time, 36.2 minutes. The standard deviation for this group was thirty-four and the range extended.from five minutes to one hundred thirty-four minutes. In the second sample the seventeenayear-old trainees had the smallest mean practice-time, 35.0 minutes. The standard deviation for this group was twenty-six and the range was five to one hundred thirty minutes, respectively. The sixteeneyear-old trainees group had the largest mean practice-time, h0.5 minutes. The standard deviation for this group was 16.3, and the range was fifteen to seventy-one minutes. TABLE I THE PRACTICE-TIME IN MINUTES REQUIRED BY FIVE AGE GROUPS TO DEVELOP THE SKILL MAKING A FIIIET4NELD LAP JOINT Groups Number Mean Range SD Fourteeneyear-old (1) lb 26.1 6-5h 13.6 trainees (2) 6 36.8 17-75 19.9 Fifteenqyear-old El) 20 31.h h-lOO 23.8 trainees 2) 15 36.9 11-90 19.5 Sixteenqyear-old 21) h? 35.6 h-125 33.0 trainees 2) 19 h0.5 15-71 16.3 Seventeenpyear-old (1) 32 36.2 5-13h 3h.0 trainees (2) 10 35.0 9-95 26.0 Eighteenqyear-old and- (1) 16 35.8 5-116 30.6 over trainees (2) 16 37.2 7-85 21.8 note: Rows (1) contain.values from.the first sample and rows (2) contain values from.the second sample. The question to be answered for both samples is, "Are the differences among the means of the practice-time for'the five age groups significant differences?" In Table XI is shown the analysis of variance, leading to a test of the hypothesis regarding the skill of making a filletdweld 62 lap joint. It can be observed in Table XI that for the first sample, 63 the ratio of the between-group variance to the within-group variance produced .368 as the value of F. Since the value of F is consider- ably less than the value of F which would be Observed in.five per cent of all random.samples from.the same normal pepulation, the hypothesis was not rejected. TABIE XI ANALYSIS OF VARIANCE OF PRACTICE-TIME IN MINUTES USED BY TRAINEES IN FIVE AGE GROUPS T0>DEVELOP THE ABILITY OF MAKING A F ILIET—WEID LAP JOINT WITH THE ARC WELDER Source of Sum of Degrees of Mean Square ‘Variation Squares Freedom. Variance F First Sample Total 111157736 128 Betweenpgroup 1,3h5.83 h 336.h6 , .368‘I Within-group 113,231.10 121; 913.16 Second Sample Total 27,767.531 65 Betweenpgroup 2h3.797 h 60.6h9 .1ll** Within-group 27,523.73h 61 [151.208 t“ L -—‘—-; ‘ ‘ *Z- r 1 r — *The value of F for the first sample must exceed or equal to 2.hh to'be significant at the five per cent level with h and 12h degrees of freedom. *eThe value of F for the second sample must equal or exceed 2.52 to be significant at the five per cent level with h and 61 degrees of freedom. 8 Table II shows, for the second sample, the analysis of variance of the practice-time in minutes used by sixty-six trainees in.five groups to develOp the ability to make a filletdweld lap joint with the arc welder. It is shown in the table that the ratio of the between-group variance to the within-group variance produced .111 as the value of F. Since the value of F does not equal to or exceed the value of 2.52, the value of F which would be observed in.fiwe per cent of the random.samples from.the same normal population, the hypothesis as applied to the skill, making a filletdweld lap joint was not rejected. Discussion and interpretation. It will be observed that in the tables setting forth the analyses of variance the withinpgroup mean squares were larger than the betweenpgroup mean squares for each skill in the first sample and for three skills in.the second sample. The question naturally arises as to whether the estimates of population variance based upon means, were significantly smaller than the estimates of population variance based upon the pooled variation'withinpgroups. A test of significance is provided by calculating F as the ratio of the withinpgroup mean square to the betweenpgroup mean square, and entering the Table of F with the degrees of freedom.reversed, that is, by determining the rejection region by the value F for which the degrees of freedom for the withinpgroup is taken for the larger mean square. The reciprocals of F, for the first sample, were found to be h.679, 2.325, 1.583, 65 and 2.71h for Tables V, VII, IX, and II, respectively. To have been significant at the five per cent level, the values of F would have been equal to or exceeded 5.66. For the second sample the withinpgroup mean squares were larger than the between-group mean squares in Tables VII, II, and XI, and the reciprocals of F were found to be 1.h86, 1.5611 and 7.h39, re- apectivelyt To be significant at the five per cent level for the degrees of freedom here available the value of F must equal to or exceed 5.70. Only the reciprocal of F for Table II was significant at the five per cent level.’ The reason.for the restriction.from group to group is not apparent. Certainly nothing was consciously done that should produce this result. There is the possibility that the sample chosen was actually an unusual one in a probability sense. Probably, under circumstances similar to those prevailing in these Observations, and with this particular skill, it is, natural for individuals within groups to vary more than the means of the groups vary around the mean of all the age groups. Investi- gation of this hypothesis is suggested as a subject of further inquiry. The large standard deviations of the groups in both samples for most of the skills are indications that the groups were quite variable. The investigator interpreted the results that have been presented regarding the means of the five age groups to mean that the evidence that their means are different is not convincing. NOr is there convincing evidence that there were circumstances present which tended to restrict the variation from one age group to another age group. Trainees' Knowledge of Arc Welding and Practice-Time The investigator wanted to know if the practice-time required by the trainees who had knowledge of arc welding before participa- ting in the study was significantly different from that of the trainees who did not have knowledge of arc welding before participating in the study. To help answer this question the trainees were divided into two groups. Che group was composed of trainees who had knowledge of arc welding before participating in the study. There were seventy-four trainees in this group in the first sample and thirty-seven trainees were in this group in the second sample. The other group was composed of trainees who were without knowledge of arc welding before participating in the study. There were fifty-five trainees in this group in the first sample and twenty-nine trainees were in this group in the second sample. It can be seen in Tables XII and XIII that the group of trainees with a knowledge of arc welding required a smaller mean practice-time than the group of trainees that was without knowledge of arc welding for all but one skill. in each sample. The group that was without knowledge of arc welding had a smaller mean practice-tine than the group with knowledge of arc welding for the 67 skill, making a filletaweld lap joint in the first sample--shown in Table XII—and for the skill, making a fillet weld in the second sample-shown in Table XIII. There were differences between the means of the two groups for each skill in both samples. To determine whether these differences were significant, a null hypothesis regarding each of the four skills was formulated and the standard error of the difference between the means was used to test each null hypothesis. For the degrees of freedom available, the values of t which would be exceeded not more than five per cent of the times in sampling from.the same normal population, are 1.979 and 2.000 for the first and second samples, reapectively. . It can be seen in Table XII that the differences between the means of the two groups ranged from 8.0 minutes for making a bead to .6 minutes for making a filletaweld lap joint. In Table XIII, for'the second sample, the differences between the means of the two groups ranged from 19oh minutes to .1 minute for the four skills. In both samples the differences between the means of the two groups decreased in the order that the skills were performed. For the last skill that was developed, making a filletdweld lap joint, the difference between the means of the two groups was less than one minute in both samples. The decrease in difference between the means indicates that the two groups of trainees probably became more alike as they practiced to develop each preceeding skill. Some of the 68 decrease in the differences between the means can probably be attri- buted to the fact that most of the manipulations of the electrodes and electrode holder required to perform each skill had been utilized in the previous skill or skills. The mean practice-time of the groups that had knowledge of (arc welding was consistently less for most skills than that of the groups that did not have knowledge of arc welding. This fact would probably lead one to think that these differencesbetween the means of the two groups cannot be unimportant even though they are not significantly dif- ferent statis ti cally . y_a_1c_i_n_g a bead. The hypothesis that was tested regarding making a bead was stated as follows: The difference between the mean practice-time required to develop the ability to make a head by the trainees who were without knowledge of arc welding and the mean practice-time required to develop the ability to make a head by the trainees who had knowledge of arc welding is not significantly different. ‘ For the first sample, it is shown in Table XII that the trainees who were without knowledge of arc welding required a mean practice-time of 55.1; minutes to develop this skill. The trainees who had a knowledge of arc welding required a mean practice-tine of only [£7.11 minutes to develop the skill. The difference between the mean practice-time of the two groups is eight minutes and the calculated value of t is .675. Since the calculated value of t is 69 Amps” peso use seam can we undefimflewwm on on mum.H vomoxe no op Hades ewes a mo asambw NNH I someoum mo nmenmon {I'll I 11" I'll So. 0.0 came? ~43 sewage” 9mm e53 a3. caefeeflfl a mag: 08. a; mafimmfl 92 Exam.” m4; Sea $3 a made: 30. i: 33% +12 fitmmm m.mm Ba. Sade a miss“ Re. o.» «363 4.2 «8&5 fimm 38. a mag *p means one monwevm meme: moemevm enema .1: e838 no 5m as 5m consummmfln {wefieamz one ‘wqfleaes naawxm no oweeazonx one no omeeazonx fie: me Sauna pdozpaz mandamus 1h“ mum2mm nadvczHqu3_om< m0 mammnzozx BDOEBH3.mmm2.om3.wMHZHde athuHBMHm Hm CZHQHmz.om< 2H mAAme mach moqmbmn OB omm: MEHBIMOHHo¢mm mma ho mzmmiHBmHma nz< UZHQHm3.om< ho Hagan EDGE; Mmmz 0E5 mmngs MZHZIHHZME. Hm UZHQHMS omd ZH QUE mbom mOAMbmn OH mam: mZHBImuHBoo.n assoc mom one: on» 0.0 psmowmwcmam an, 3. 3m; 0838 .8 flags page 9 mo 03w? EH I Housman Ho 30.“on 4mm. 0;. 80.8 H00 mm ~33: tam 0a sfion a3 fission?“ a made: an”. «A 08.3.“ :00 8 333 3.0 .3 3o... 35 s would.” Em. m5 818“ SM Hm $0.8m 0.3 me So: song n mesons RN. m.~ Stein imm a. $0.3m 0.3 R neon s wanes...“ *0. evade agenda 5“ z messiah moaned: a.“ z needed: 5 no adm mane: mo 5m enema memes e5 smegma Seesaw new 55% new ndhflm ooseuomfin «8.3.95 mnoaop of hen soaemnemsosg 05 an... mcwowpoeea semen 0b: 36 one mosses: hep 93 35.30.03 demon on: 38.35. gm emmHm I 2E0 m3» zoggmzozmn ES. H3 ME. GZHOHaofla ZHGMm Roz GHQ om? mama/fig 924 2E0 23 zoggmzozma WE. Had was OZHUHBOEA 25mm OE.» EH55. Hm OZHSMS omd 2H magma 5.5% mag 09 ammHDOmE galmogoém ME. mo mzfimz zgmm EzmmmeHn 85. mo MOEOHEOHm E 339 practice-time of 51.3 minutes to deve10p the ability to make a fillet weld. The number of days between the demonstration and the beginning of the practice-time for this group ranged from one to twenty days and the mean number of days between the demonstration and beginning practice was h.h. The difference between the mean practice-time of the two groups was h.5 minutes. In the second sample, as shown in Table XV, thirty trainees began practicing the day the demonstration was given. This group of trainees required a mean practice-time of hl.8 minutes to develop the ability to make a fillet weld. There were thirty-six trainees in the group that did not begin practicing the day the demonstration was given. This group required a mean practice-time of 52.5 minutes to develop the ability to make a bead. The number of days between.the demonstration.and the beginning of the practice-time ranged from.one to ten and the mean number of days between the demonstration and beginning practice-time was 2.7. The difference between the means of the practice-time for the two groups of trainees was 10.7 minutes. Making a butt weld. In the first sample, which is shown in Table XIV, sixty-nine trainees began practicing the day the demonstration was given. A mean practice-time of 37.2 minutes was required by this group to develop the ability to make a butt weld. There were sixty trainees in the group that did not begin practi- cing the day the demonstration was given. A mean practice-time of 78 1,9 79 .Ho>QH #:mo 9mm obflm one no endowmacmam 09.09 ooo.m vomoxo no Hades pde 9 mo mBHm>* .40 I acumen“ mo moonmmn Re. 06 S33 15 mm £12 33 em efion em: . 33532“ e mafia: mg. «.3 ahead 04m am Show 93 mm 33 3.5 a mega: as. toe 30.3 m.mm on 93.8 93 on So: e233 a mess: gm. doe 235 tom an 33.3 0.3 an 38 a magma a» awesqfis ma moeesvu mopsqde ea 2 mousse» mopenfls ea 2 means use me 35m muses mo.3:m enema newness ambfim as: . nebfim we: oocmhomman nowpwhpmaoaov one awe soapdhpmcoaou on» mHHme esp mewOfipodua demon pom pee on: newsflash IIHIH‘ III‘ and one madcapooem semen on: noosfiaha mumzHw m43,20HBdmamzosz may Mdm mma 02HOH80¢mm zHomm Roz GHQ om3_mMMZH4me Q24 zmme m¢3.20HBma OB QMmD MEHBIMOHBUmn OB nmm: MZHBIMUHao¢mm mma mo wzH mHm<9 W 88 Observed between the means of the practice-time required to develop each of the skills was .9 minutes. This difference was Observed for the skill making a bead. The largest difference between the means of the practice-time Observed was 9.8 minutes. This difference was for the skill making a filletaweld lap joint. However, none of the differences recorded in Table XVII were significant at the five per cent level. In view of the fact that there were no significant differences between the means of any skill for the two samples, it is suggestive that the samples might well have come from the same population therefore they may be combined. Practice-Time Required to Develop Four Skills In view of the fact that there were no significant differences between the practice-time means of the groups within the two samples and there were no significant differences between the means of the two samples it is appropriate to combine the data of the samples and calculate a mean for each of the four skills. The fiducial limits shown in.Table XVIII defined a random interval which may be said to enclose the population mean unless the sample is more unusual than.five out of every one hundred samples from a normal population. It may be said that the best average estimate of the mean practice-time required to develop the ability to make a bead with.the arc welder is 50.32 minutes and MEAN PRACTICE-TIME IN MINUTES REQUIRED BY 195 TRAINEES TABLE XVIII TO DEVELOP FOUR SKIIIS IN ARC WELDING ‘—~—> Skills Mean SD SD; Eiizgial Lfigizi making a bead 50.32 39.08 2.700 hh.8h 55.81 Making a fillet weld h8.37 38.97 2.792 82.90 53.8h Making a butt weld h0.38 27.95 2.002 36.h6 hh.30 Making a filletaweld 18p Joint 35.33 26.99 1.933 31.5h 39.12 89 L that it is not less than hh.8h minutes nor greater than 55.81 minutes. In general the fiducial limits were relatively narrow, the smallest being 31.5h minutes and 39.12 minutes for the skill making a filletdweld lap joint, and the largest being hh.8h minutes and 55.81 minutes for the skill making a bead. The two intermediate values, h2.90 minutes and.53.8h minutes, and 36.h6 minutes and hh.30 minutes were for the skills making a fillet weld and making a butt weld, respectively. It will be observed that there was tendency for the fiducial limits to be smaller for the smaller means. It will be recalled that the skills are listed in the tables in the order in which they were performed. Inspection of Table XVIII shows that the mean practice-time decreased as a new skill was 90 introduced. In this connection, attention is called to the fact that the manner in which the electrode should be manipulated is similar in each of the four skills, therefore, with continued practice one should expect a reduction in the time required to de- velop each of the succeeding skills. The pattern that prevailed in 1 regarding the effects of practice. He said, “If a person can perform a manual the study is in accord with the statement made by Barnes task at all, he can reduce the time per cycle for performing it with practice.” Reliability and.Validity of the Method One of the problems of the study was to find an answer to the question, Is the method that was used to collect data for the study reliable and valid? The instrument2 used to collect data was develOped by the author and it was used for the first time in this study. Two of the most important considerations in the construction of an instrument of this nature are that it shall have reliability and.validity. Evidences found in the study will be used to answer the question, Does the instrument have reliability and validity? Reliability. The instrument is reliable if it gives the same 1“Ralph M. Barnes, Motion and Time Study (New York: JothWiley and Sons, Incorporated, 1950), p. D96. 2See Appendix A. 91 results consistently. The detect the study do not make it possibleto state an estimate of the coefficient of reliability'of the instrument. How- ever, it is shown in Table XVII that there is a lack of significant differences between the sample results Obtained by teachers who did have and teachers who did.not have experience and supervision in the administration of the instrument used in the study. These two groups of teachers used the same instrument but they worked separately, at different times, and with different trainees, yet the results Obtained by the two groups were very much alike. Therefore, the claim that the instrument is reliable to a satisfactory degree is not without some justification. Validity. An instrument is valid if it measures what it is supposed to measure. In this study the instrument was supposed to measure the time required to develop four basic skills in arc welding. Regarding the validity of tests Nelson and Denny say, Validity of tests is frequently discussed under two sub-divisions; namely, curricular validity and statistical validity. If there is agreement between the material found in the test and the material which the pupils were assigned or ex- pected to master, the test has curricular validity. The fact is usually'noted by inSpection of the materials rather than by statistical procedures, 3M. J. Nelson and E. 0. Danny, 5 gacticel Guide and workbook i2 Statistics for Teachers (New York: The Dryden Press, Incor- porated, 1950), p. 137. 92 Evidence of curricular validity of the instrument used in the study is inferred in the fact that the steps which constitute a part of the material in.the instrument are in complete agreement with and identical to the material which the trainees were expected to master. The basic steps involved in manipulating the electrode in arc welding are repeated in each of the skills used in the study. These basic steps are parts of the job such as, adjusting the amperage setting, striking the arc, establishing the bead, etht Also, it is logical to expect that as more skills are developed which utilize the same basic steps in the same position there should be a decrease in the time required for practice to develop each of the successive skills. It is shown in Tables XVII and.XVIII that there is a decrease in the time required to develop each successive skill. Since there is agreement between the material in the instrument and the material which the trainees were expected to master, and since the results Obtained from.using the instrument took the form that would logically be expected, this is suggestive that it is not unreasonable to infer that the instrument is valid. Summary Forty-three teachers of vocational agriculture and one hundred ninety-five trainees participated in the study. Two samples were 1‘See Appendix A, JObs number 1, 2, 3, and h. 93 taken. In the first sample there were one hundred twentyanine trainees. In the second sample there were sixty-six trainees. The individuals in the second sample performed under close supervision of the investigator. The mean practice-time of the trainees was compared for each skill in both samples. No significant differences between the means of the age groups were found within either sample for any of the four skills, nor were there significant differences between the means of the two samples for any of the skills. The relationship between the practice-time required by the trainees to develop the skills and the time the teachers used to demonstrate the skills revealed positive but low coefficients of correlation for each skill in both samples. Estimates of the mean practice-time required to develop each of the four skills; making a bead, making a fillet weld, making a butt weld, and making a filletdweld lap joint, were observed to be 50.32 minutes, h8.37 minutes, h0.38 minutes, and 35.33 minutes, respectively. The reliability of the instrument is reflected in the close similiarity of the results Obtained in the two samples. Evidence of validity is suggested in the agreement of the material in the instrument with the material that the trainees were expected to master and in the logical results obtained from.the use of the instrument. CHAPTER‘V SUMMARY AND CONCLUSIONS The major problem.of the study was to find an answer to the question, HOw much time do students of vocational agriculture re- quire for practice to develop each of these basic skills in arc welding, (1) making a bead, (2) making a fillet weld, (3) making a butt weld, and (h) making a filletdweld lap joint? Subsidiary problems of the study were to find answers to the following ques- tions: 1. Is the time that students require for practice to develop the basic skills in arc welding associated with the age of the students? 2. Is there a difference between the time required for practice to develop the basic skills in arc welding by those students who were without.knowledge of arc 'welding and that required by those students who had knowledge of arc welding? 3. Is the time that the students required for practice to develop the skills in arc welding associated with the time used by the teachers to demonstrate the skills? b. Is there a difference between the time required for practice to develop the basic skills in arc welding by those students who began practicing the same day the demonstration was given and that required by those who 5. 95 did not begin practicing the same day the demonstra- tion was given? Is the method that was used to collect data for the study reliable and valid? The purposes of this chapter are (l) to summarize the findings of the study concerning the practice-time required by one hundred ninety-five trainees to develop the ability to perform four basic skills in arc welding, and (2) to set forth the conclusion made in light of the interpretations given to the findings. The trainees in the study were students enrolled in vocational agriculture classes in five states. Summary. What appeared to be important findings are summized as follows : 1. The mean practice-time required by the trainees to develop 2. each of the four skills in arc welding were: a. For making a bead, 50.32 1- 5.h9 minutes. b. For making a fillet weld, h8.37 * 5.147 minutes. c. For making a butt weld, 140.148 i 3.92 minutes. 6.. For making a fillet-weld lap joint, 35.33 i 3.79 minutes. The variations among trainees in the practice-time required to develop the ability to perform each of the four skills in arc welding were large. The individuals within the age 96 groups varied more than the means of the groups varied around the mean of all the age groups for the time re- quired to develop most of the basic skills used in the study. The ages of the trainees ranged.fr0m.fourteen years to forty-one years. The study showed that there were no significant differences among the means of the practice- time required by the trainees of five age groups to develOp any one of the four skills. The mean practice-time required to develop each of the four skills by the trainees with a knowledge of arc ‘welding generally was less than that of the trainees who did not have knowledge of arc welding, however, there was no significant difference between the means of the two groups for any one of the four skills. There was a low positive association between the practice-time required by the trainees to develop each of the four skills and the time utilized by the teachers of vocational agriculture to demonstrate each skill. The mean practice-time required to develop each of the four skills by the trainees who began practicing the day the demonstration was given on an average was less than that of the trainees who did not begin practicing 97 the day the demonstration was given, however the difference between the means of the two groups was not significant for any one of the four skills. 7. The teachers of vocational agriculture and the trainees in the second sample participated under closer super- vision of the investigator than.those who participated in the first sample. There was, however, no significant difference between the means of the two samples for the practice-time required to develop any one of the four skills. 8. There are evidences in the study that the method used to collect data has reliability and validity. Conclusions. In light of the findings in the study it seems justifiable to conclude that: 1. For populations of students in farm mechanics of which this sample is representative, approximately one hundred seventy-five minutes should, on an average, be sufficient for developing the four basic skills in arc welding. Two implications that can be drawn from this statement are as follows: a. Teachers of farm mechanics planning their schedules so that approximately one hundred seventy-five minutes are provided per pupil for practice-time to develop the abilities to, (1) make a head, (2) make a fillet weld, (3) make a butt weld, and (h) make a filletaweld lap joint, will on an average, have allowed sufficient time for the development of these skills. b. School administrators who provide welding madhines and supplies, so that each pupil can, (1) use them. for approximately one hundred seventy-five minutes for practice to develop the four basic skills in arc welding, and (2) begin practicing on each skill within four days after it has been demonstrated, have provided sufficient facilities for arc welding in the farm mechanics classes. 2. 0n the basis of the evidence available one cannot be disposed to teach the basic skills in arc welding to students of one particular age group in preference to any'other age group for the sake of economy of time. In accordance with the inference that can be reasonably drawn from the study it would follow that instruction aimed at developing the basic skills in arc welding may be profitably planned for any group enrolled in all-day or young farmer classes in vocational agriculture. 3. In populations in which the samples of students under study are representative, those students who gain knowledge of arc welding by Observation only or by 98 gel} '“M‘O‘r't ‘r 99 helping someone weld but without practice will not, on an average, develop the basic skills in arc welding with any less practice than those students who have not gained such knowledge. It logically follows, there- fore, that the practice of having students watch others weld seems to have very little value as far as helping E K them develop the welding skills faster if they have not . I been given instruction on what to observe during the process. Teachers cannot be sure of reducing the practice-time V 9 required by pupils to develop the basic skills in arc welding by giving longer demonstrations. The results of this investigation did not provide convincing evi- dence that there was any worthwhile association between the practice-time required by the students to develop each of the skills and the time utilized by the teachers to demonstrate each skill. It appears that the portion of the variation in_the amounts of time teachers spent in demonstrating eaCh of the skills which is associated with the variation in the amounts of time required by the students to develop the skills is, in a probability sense, too small for practical purposes of prediction. On the basis of the evidence Obtained in the study, for populations in which the samples of students under study 100 are representative, when the mean number of days between the demonstration and the day the students begin prac- ticing is no greater than four it can be reasonably expected that the students will develop the ability to perform each of the basic skills in arc welding on an average as quickly as those students who began practicing on the day the demonstration was given. One implication drawn from this statement is that it would probably be most expedient if the students begin practicing for the development of a skill in arc welding within four days after the skill has been demonstrated. Another implica- tion of the findings of the study is that further investigation should be made to determine the true differences between the practice-time of students who begin practicing immediately after the demonstration and that of those students who do not begin practicing im- mediately after the demonstration to develop skills in arc welding. Further inquiry should be made to determine if it is natural for individuals within the age groups, as defined in this study, to vary more than the means of the groups vary around the mean of all the age groups for the time required to develop the basic skills in arc welding. 7. FUrther study should be made to determine the relation- ship of grade level of students to the practice-time required to develop the basic skills in arc welding. 8. It is recommended that the method used to collect data for this investigation be used to make further inquiry into the time required to develop arc welding skills and skills in other areas of farm mechanics. 101 . .) -383“. is] ' 5‘ BIBLIOGRAPHY A. Books Arkin, Herbert and Colton, Raymond R. Tables for Statisticians. New York: Barnes and Noble, Incorporated:'l956. IS? pp. Austin, John Benjamin. Electric Arc‘Welding. Chicago: American Technical Society, I952. 285 pp. 102 Barnes, Ralph M. Motion and Time Stud . New York: John Wiley and Sons, Incorporat53,'l§30. 5 pp. _g_ . MOtion and Time Stud Applications. New York: John Wiley and Sons,-I§h8. 188 pp. Book, William F. The Ps cholo 2f Skill. New York: The Gregg Publishing Company, l§§5. Chaffee, Wilbur Johnson. Practical Arc'Wel . Troy, Ohio: Hobart Trade School, IncorporatEd: . 516 pp. Crawford, Claude C. The Techni uepgf Study. New York: Houghton Hifflin Companyf'l‘ng—E‘S'g". pp. Croxton, Frederick E., and Cowden, Dudley J. gpplied General Statistics. New York: Prentice-Hall, Incorporated, l9h6. Educational Objectives in‘Vocational Agriculture. ‘Washington: U. S. Office of Education, Vocational Division.Monograph No. 21, Revised 1955. 1h pp. Good, Carter V., Barr, A. S., and Scates, Douglas E. Methodolo of Educational Research. New York: Appleton~CenturyaCrosts, Ticorporated:_l95l. 890 pp. Hagood, Margaret Jarman and Price, Daniel 0. Statistics for Sociologists. New York: Henry Holt and ”Mommy, 95?? PP- Hollenberg, Alvin.H. .EE!.ZB Teach Arc welding i§.Farm.Mechanics. Cleveland: The James F. Lincoln Arc'Welding Foundation, 1952. 56 pp. :‘A ” i "— l‘s 103 Huggett, Albert J ., and Millard Cecil V. Growth and Learning in the Elementary School. Boston: D. C. Heath and Company, I9E6T’ hlh pp. Jefferson, Theodore Brewster, and Woods, Gorham. Metals and How to Weld Them. Cleveland: The James F. LincoE Arc Wain} Fsundation, 195k. 322 pp. Kugler, Harold L. ‘érg‘Welding Lessons £25 School 229 Farm Sh . Cleveland: The James F. Lincoln Arc welding Foundation, E950. 3&3 pp. Millard, Cecil V. Child Growth and Development in the Element School Years. Boston: D. 57—Heath and Company, 1951. SEE pp. Morford, Vilas Jay. Farm 533 Welding. Cleveland: The James F. Lincoln Arc'Welding Foundation, 195k. h56 pp. Munn, Normal L. "Learning in Children," Manual of Child Psychology, Edited by Leonard Carmichael. New York: John'Wiley and Sons, l9h6. 1068 pp. Nelson, M. J., and Denny, E. C. 'A‘Pgectical Guide and'WOrkbook'ip Statistics for Teachers. New York: The Dryden Press, Incor- porated, 1950: 199 pp. Phipps, Lloyd J., and Cook, Glen C. A Handbook on Teac ' Vocational Agriculture. DanvilIE, Illinois?— The gnEerstate 'Printers and—Publishers, 1952. 1023 pp. , and others. Farm Mechanics Text and Handbook. Danville, Illinois: The Interstate Printers and—Publishers, 195k. 752 pp. Procedure Handbook gf‘érg'welding Design and Practice. Cleveland, Ohio: The James F. Lincoln Arc woidifig Foundation, 1950. 1200 pp. Snedecor, George. Statistical Methods. Ames Iowa: The Iowa College Press, Fourth edition, 19h6. h8 pp. Snowden, Obed L., Cook, Glen 0., and'Walker, Clyde. Practical Methods ig.Teac Farm.Mechanics. Danville, Illinois: The Interstate P nters and—Publishers, 1952. 658 pp. walker, Helen M. Element Statistical Methods. New York: Henry Holt and Company, I953. 358 pp. 101: B. Periodicals Albrecht, Carl F. "Development and Application of Farm Mechanic Skills and Judgments,n Agricultural Education Magazine, 25:68, September, 1952. Burt, Fred M. "Gas Company Trains Its Own‘Welders,"‘Welding Engineer, 36:h0, June, 1951. . "Stomach Education in'Welding,"'We1ding Engineer, 835532, September, 1950. Fuller, R. L. "How Good Are Your Welds?" ‘Welding Journal, 29:77h, September, 1950. Pyle,'W. H. "Concentrated Versus Distributed Practice," The Journal 2: Educational Psychology, 5:2h7, 191h. Slater, S. J. “Training Aims at Basic Skills," Welding Journal, 19: 637, September, 19140. 'Willgoose, Carl E. "The Relationship of Muscular Strength to Motor Coordination in the Adolescent Period, " Journal of Educational Research, hh: 138, OctOber, 1950. Young, Orville L. "What Are They Teaching in Farm Mechanics?" Agricultural Education.M§gazine, 23:208, March, 1951. C. Unpublished Materials Clanin, Edgar. ”The Development of A Device for'Determining the Farm—Job Experiences of Students of Vocational Agriculture.” Unpublished Doctor's dissertation, Purdue University3‘West Lafayette, Indiana, 1951. 133 PP. Dougan, Riley Shelton. "Farm.Shop Skills and Abilities Needed and Acquired by Beginning Teachers of Vocational Agriculture in Ohio." Unpublished Master's thesis, The Ohio State University, Columbus, 1951. 139 pp. Schafer,‘Wa11ace A. "Teaching Units in.Farm.Mechanics for Courses of Study in Arizona Departments of Vocational Agriculture." Unpublished Master's thesis, University of Arizona, Tucson, 1951. 99 pp. 105 D. Report Report of the subcommittee on Agricultural Teacher-training, Committee on Curriculums (College Division), American Society of Agricultural Engineering, in Collaboration with an.Advisory Group of Agricultural Education Specialists, submitted June 22, 19kt. 106 INSTRUCTIONS 1'2 THE TEACHER Certain uniform procedures for teaching these skills are believed to be necessary, therefore, the teacher is requested to follow the procedure given below in his natural teaching manner. A. D. G. Selection of trainees. Give a copy of Form.1 to persons in the class whomfyou think have not done any welding and ask them to fill out Part I and return it to you. Select as trainees those who marked "x" in front of items 1, 2, or 3 and agreed to keep a record of the time they will practice. Dress for the demonstration. ‘Wear gloves and dress so that you will'protect your body and clothing while giving the demonstration. Preparation before_the trainee§_are assembled. Lay out near the welding machine and table all the tools, materials and equipment that will be needed for the demonstration. Have practice material and a copy of the Job Breakdown ready to give to the trainees after the job has been demonstrated. Some practice alone prior to giving the demonstration.may be helpful also. Assembling trainees for demonstration. Have the trainees assemble in’a semi-circle about the welding table. Do not disturb other members of the class who may be working in other areas. Recording_the time. Nets time of beginning and ending of demon- stration. Record the amount of time used in the blank space to the right of item.h, Part II on Form.1. Instruct the trainees to keep a record of the time, in minutes, they Spend practicing and record it in the space to the right of item.3, Part II on Form.1. Have the trainees fill in the spaces opposite items 1 and 2, Part II on Form 1 and return it to you. (Do not include time Spent by trainees in reading, securing information and preparing the metal for welding or inspecting the weld.) Checking and returning the forms. Examine both parts of each ferm.for completeness and accuracy and return them.in the stamped envelOpe. Procedure for demonstrating the obs. (Use the same basic pro- cedure for demonstrating each 30 . After the trainees are assembled, get them interested in learning how to do the job. *After a reasonable length of time (to be determined by the teacher), if the trainee has not produced a specimen weld that meets the criteria set up, have one of the other trainees begin practicing. 107 (This part is extremely important since much of the effectiveness of the lesson depends upon the extent to which this is realized.) The following steps are suggestive of a procedure that may be used to accomplish this for the first Job; Striking an arc and running a bead. 1. Use regular teaching manner to make trainees feel at ease. 2. Impress upon the trainees that they are to work for the perfection of good welds rather than for speed. Quality of the work that they produce is of prime importance, however, they should try'to learn how to make the bead as quickly as possible for their own benefit. ”The problem method or any other method that the teacher has used successfully to arouse interest.might well be used to introduce the lesson. Some suggested questions are as follows: a. In what ways do you know of welders having been used to repair or construct farm equipment? (If no answers are given, the teacher should bring out the point that rejoining broken metal parts, strengthening worn parts by building them up, joining metal parts quickly, etc., are some of the ways that they may be used.) Examples Should be given. b. If you know how to use this welder what are some of the jobs that you would like to do with it? (let two or three of them tell about the things they would like to make or repair. The teacher might cite examples of things that others have done to bring out the point that knowing how to weld is an asset to the farmer and that to learn.how to weld skill- fully is not too difficult.) c. How do you.think that you can best learn to use this welder successfully and properly? (In securing the answers be sure the point is brought out that good arc welding is the result of several basic operations, some of which are: (1) Using the right kind of electrode (2) Proper cleaning and preparation of the metal (3) Setting the machine preperly (h) Striking and maintaining the right arc length (5) Running the bead at the correct speed 108 Also bring out the fact that after one learns what to do, one must also learn hngto do it best. The best way for one to learn how to weld is to practice welding properly. Show specimen of good.welds, point out their characteris- tics and explain how they were produced. h. Giving the first demonstration* a. Give each trainee a face shield or helmet to observe the demonstration. b. Explain to the trainees that.you are going to give them a demonstration on how to strike an arc and run a bead, they are to Observe eadh step and ask questions about anything they do not understand. c. Tell what is being done as each step is performed. Use key points and eXplanations to bring out hgg_and why the step is performed in that manner. Explanations Usually, thick metal and large electrodes require high amperages while thin metal and small electrodes require low amperages. An amperage setting of 125 is a good one to use on a trial bead for . 5/53" electrode and 3/16* mild steel. If too high, it should be decreased. If too low, it should be increased. Good surface contact of the metal conductors is essential if an adequate and.even flow of electricity is to pass between the elec- trode and the practice plate to produce a good arc. Clamping the plate to table top increases surface contact. When the bare end of the electrode is placed between the jaws of the holder, metal contact is made that will allow electricity to pass through the electrode freely. This is essential to produce and maintain a good arc. Turn the welding machine on when you are ready to weld and turn it off when.you have stopped. This is for the protection of the people about the welder and the welding equipment. *Follow the same basic pattern in giving each of the four demonstrations. 109 By holding the electrode almost vertically above the plate, it is easier to strike the exact point desired after the helmet is pulled over the face. ‘With the helmet or shield in position over the face the welder cannot see until the arc lights up the work. Be sure that everyone who is observing has a shield over his face before striking the arc. Holding a long are momentarily after it is first started gives it time to heat up the metal and reduce freezing. By holding the electrode at an angle of about 20 degrees in the direction that the electrode is being moved, one can see the arc, the pool of molten metal and the width of the bead being formed. In this manner one can see when the bead is about the same width as the coated electrode. This helps in judging the correct speed. One can see how fast the electrode is melting and therefore more accura- tely judge how fast to feed it down to the plate. APPENDIX A THE INSTRUMENT used TO COLLECT DATA 110 Form 1 PART I. CLASSIFICATION OF TRAIIEE Name Age (Years) All Day Class Isobar? __ Young Farmer Class llamber? Directions: Put a mark (X) on the line to the left of the statement below that more nearly describes your experience or lack of experience in electric arc welding. l. I have never done any electric arc welding and do not know how it should be done. 2. __ I have never done any electric arc welding but I have seen it done or have seen someone demonstrate how to do it, however, I do not know whether it was done according to the best methods or not. 3. I have never done any electric arc welding alone but I have, helped someone also frequently, however, I do not know whether the welding was done according to the best methods or not. Do you agree to keep a record of the amount of time in m spent practicing on each arc welding Job and write it on the form balovf? Yes No PART II.: REmRD OF PRACTICE TIIE —th M” Bead leld wold I4'19 Joint Joint Jalnt 1. Did you begin practicing Yes imadiately after the N M7 ° 2. If answer to item 1 is no, how long was it before you D‘YS 3. How much time did you spend practicing before doing Minutes 4. How much time was used to Minutes W mmmnmm-A Form 2 111 INSTRUCTIONS FOR TRADEES AFTER MAXIM; A EAD D CT 0N5: After cleaning the bead examine it and compare it with the photographs and characteristics below. If the appearance of the bead is 32; very much like the top photograph, compare it with the others and their characteristics to help determine the cause of the defective con- dition. Make the necessary adjustments and run another head. When you have made two beads consecutively with characteristics and appearance very much like the top photogiaph and they are approved by the teacher, on F0 m the a 0 me ha 0 ev d 0 ac ce (JDMMON CHARACTERISTICS OF TFE BEAD ‘ ' 1. Bright surface with uniform ripples. 2. Edges smoothly joined to the plate. 3. Fairly deep crater at end of bead. 4. Very little spatter. (Good normal bead)* 1. Metal piled up excessively high. 2. Deposited metal may overlap plate. 3. Lack of penetration along edges. 4. Wide bead. (Slow speed of travel bead) 1. Elongated ripples on the surface. 2. Bead is small and narrow. 3. Fusion along edges not smooth. 4. Penetration not uniform along edges. (Fast speed of travel bead) 1. Excessive spatter on the plate. 2. Undercutting along the edges. 3. Deep penetration. 4. Long crater at end of bead. (Hot bead, too much amperage) 1. Poor fusion along edges. 2. Shallow crater at end of bead. 3. Metal may overlap the plate. 4. Metal piled up excessively high. (Cold bead, amperage too low) l. Bead irregular in shape and size. 2. Bead is wide and flat. 3. Excessive Spatter on the plate. Wide shallow crater at end of bead. (Arc too long, other conditions may be normal) *Notex This head will also be used with Jobs Nos. --,. M4 JOB.BREAKDOIN*: 1. 2. 3. 4. 5. 6. 7. m Adjust the amperage setting on the welding machine. Prepare the welding table. Select electrode. Turn welder switch to the ”on” position. Adjust helmet on head. Strike the arc. Run the bead for a distance of about six inches on the plate b. b. b. d. 112 Striking an arc and running a good flat bead. 1521221919. Use 125 or point nearest this for trial setting. Make the ground cable connec- tions secure. Clamp the plate to the table. Use 5/32' general purpose electrode. (Type E6013) Put bare end in the holder. See that the main cable is plugged in and the current is on at the main switch. Hold tip of electrode i” above the place where bead is to begin on practice plate. Adjust helmet over face before striking the arc. Use a scratching motion or tapping motion. After striking arc, hold a long arc momentarily, before beginning to form the bead. Keep tip of electrode above crater a distance equal to diameter of electrode. Keep electrode almost per- pendicular to practice plate but tipped 20 degrees in direction of travel. ma. bead width 1} times diameter of metal electrode. Keep bead forming in straight IIDCe *Some material in the Job Breaddown has been taken from Wing ‘ngggng, Lincoln Welding Foundation. - 1 - 8. 9. 10. 11. 12. Turn the switches on the welder to the ”off position. Clean the bead. . a. Chipping be Brushing Examine the bead.* Have a trainee strike an arc and run a bead. Have trainees begin practice session. b. Ce d. b. b. Ce b. Ce 113 Hang the electrode holder. Chip away the slag formed on the bead. Chip after the plate has cooled enough for the dark natural color to return. Protect the eyes from flying scale. Handle the plate wifih pliers or tongs while hot. Follow the direction on Form 2e Compare the bead with the pictures and characteristics.. Have trainee tell and show what he is doing on second bOIde Correct errors that trainee makes. Ask questions of trainee about steps and key points to help insure proper understanding. Pass copy of Job Breakdown to each trainee. Each trainee will use same copy of Form.2 when ready to examine bead. Instruct trainees to record time on Form 1. *If the first bead is not a good one, point out the faults and defects to the trainees, explain what caused the imperfections, show them how to remedy it (or them) and make another bead. -2- JDPLNELJZ JOB BREAKDOIH: m 1. Adjust the amperage setting on a. the welding machine. 2. Prepare the welding table. a. b. 3. Prepare two pieces of metal a. for use in making the joint. Grind here b. ‘~ Figure l. - Surface to be cleaned. 4. Select electrodes. a. 5. Tack weld the two pieces of a. metal together. b. Fiture 2. e Position for tacking 6. metal plates. Strike arc and establish bead. a. b. 111; Making a single pass fillet weld in flat position. Man For the trial setting use 135 or the point nearest to this figure. Make ground cable connections 8. cure e Locate pieces of metal to hold practice plates in place while b.1159 "OldCde . Use 3/16' mild steel, preferably 1 or 2 inches wide, about 6 inches long. Scrap metal may I). USOde Clean parts where the bead will be formed. Grind until surface is bright. See Figure 1. Use 3/32' general purpose electrode. (Type E6013) Position the two pieces of metal as shown in Figure 2. Strike an arc and run a bead about'i' long at each end of the joint. Remove the slag by chipping and brushing well. Strike arc at point within one inch of the corner where weld is to begin. Bring tip of electrode into position in corner of weld Ind hold long arc momentarily. 7. 8. 9. Run the fillet weld. Electrode Figure 3. - Position of plates when running fillet ”lde Chip and clean the bead. Inspect the weld. a. Surface appearance. b. Break the weld. Movable jaw of vise Figure 4. - Breaking fillet weld in vise. b. d. b. b. d. 115 Hold electrode at 45 degree angle to plates, (see Figure 3) tipped forward about 20 degrees in direc- tion of travel. Hold electrode so that the coating is about 1/16 or 1/3 inch from plate on either side. Observe action within the pool of molten metal at all times and keep amount of deposited metal equal on both plates. If undercutting begins to appear on the righthand plate shift the point of the electrode slightly toward that plate. Slightly increase speed of elec- trode to stop piling up of metal, decrease speed if insufficient metal is deposited. Use chipping hammer and wire bNShe Protect the eyes from flying scales. Examine the bead to see if it has the appearance and characteristics very much like a good bead (see top photograph on Form 2). Place in a vise and break by striking on opposite side from weld (see Figure 4). Examine broken weld for: a ‘pgngtrgtigg. Minimum of half the thickness of each metal plate. - mummmnm. Indi- cated by clean grey metal all along the edges. Blackened condition in- dicates poor fusion. mmmmmn. Indicated by absence of slag and gas pockets on the exposed part of the deposited metal. If the broken fillet welded joint does not show indications of adequate penetration, full fusion 9. 10. 11. Continued. Repeat steps 1 through 9 until two fillet welds are made in succession that show indications of having the qualifications listed under the key points. Record the amount of time devoted to practice. Co d. Ge b. 116 along the joint, cleanliness and freedom from porosity, correct the condition that caused the defective weld and make another jOIflte Surface appearance of a normal beido Adequate penetration. Full fusion along the joint. Clean and free from porosity. Meets the approval of the teacher. Use Form Ho. 1, Part II. Fill the space for item 3 in the column with the heading "Fillet leld Joint." Return Form 1 to the instructor. Job N9, 3 JOB BREAKDOIN: .EISEE 1. Prepare two pieces of metal using the single vee method. )300 H— \ \ . Shoulder edge \ \ I l/ I l I 1 Figure 5. - Angle to grind edges of plates. ;' 2. Adjust amperage setting on the welding machine. 3. Prepare the welding table. 4. Select the electrodes. 5. Clamp the two pieces of metal in welding position. l/l6" gap between plates £%