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A comparison of Holland's model using constructs measured by two different methods
journal
of Vocational
Behavior 9, 245-250 (1976)
A Comparison of Holland’s Model Using Constructs Measured by Two Different Methods R. MONTE BOBELE North Harris County College HERBERT L. ALSTON University of Houston JAMES A. WAKEFIELD, JR. California State College, Stanislaus and EUGENE B. DOUGHTIE University of Houston
The relationship was studied between the set of constructs specified by Holland’s (1973) theory (viz, Realistic, InteIIectual, Artistic, Social, Enterprising, and Conventional) measured by an Adjective List (AL) derived from Holland’s theory and the same set of constructs as measured by the Vocational Preference Inventory (VPI). The correspondence of the two measures of Holland’s model compared the distances between the constructs as measured by the AL and the constructs measured by the VP1 in factor space using an adaptation of a model testing procedure reported by Wakefield and Doughtie (1973). The subjects were 174 undergraduates at a state university. The correspondence between the two separate measures of Holland’s model was significant @ < .Ol). These results provide further support of the construct validity of Holland’s theory and offer evidence that the relationships hypothesized by the theory are not tied to any one particular method of measurement.
Holland (1973) presented a theory of careers based on six personality types (viz, Realistic, Intellectual, Social, Conventional, Enterprising, and Artistic). The relationships among these types are specified by a hexagonal model, where the distances between the constructs in the model are hypothesized to correspond to psychologically meaningful distances. This is to say that the closer two constructs are in the model, the more similar individuals would be who correspond to these types. The relationships among the Requests for reprints should be sent to Dr. Eugene B. Doughtie, Department Psychology, University of Houston, 3801 Cullen Boulevard, Houston, TX 77004.
24.5 Copyright @ 1976 by Academic Press, Inc. All rights of reproduction in any form reserved.
of
246
BOBELE ET AL.
constructs in Holland’s model have received considerable support when those constructs were measured by the Vocational Preference Inventory (VPI) (HolIand, 1970) (cf. Cole, Whitney, & Holland, 1971; Wakefield & Doughtie, 1973; Wakefield, Yom, Doughtie, Chang, & Alston, 1974). A psychological construct is a hypothetical entity and is defined in terms of its relationship to other such constructs. Such a system of stated relationships among constructs constitutes a theory or a nomological network (Cronbach & Meehl, 1955). By definition, a construct is not synonymous with the operations by which it is measured and construct validity refers to empirical evidence for the postulated relationships among the constructs (Cronbach & Meehl, 1955). Several researchers have argued for the use of more than one method of measurement (Campbell & Fiske, 1959; Cronbach & Meehl, 1955; Webb, Campbell, Schwartz, & Sechrest, 1966) to validate a theory. To the extent that different methods of measurement of the constructs employed in a theory result in the relationships predicted by the theory, the theory is considered to be more firmly established and perhaps more general in its application. Bobele, Alston, Wakefield, and Schnitzen (1974) recently reported that Holland’s model was supported using the model testing procedure of Wakefield & Doughtie (1973); (cf. Doughtie, Wakefield, Sampson, & Alston, 1974) with constructs measured by an adjective list derived from Holland’s theory. The present study compares the relationships between the set of constructs measured by the adjective list and the same set of constructs measured by the VP1 using an adaptation of the aforementioned model testing procedure. METHOD Subjects One hundred and seventy-four students enrolled in undergraduate psychology courses at the University of Houston participated in the present study. The sample was comprised of 92 women (53%) and 82 men (47%). The mean age of the subjects was 23.7 yr and the standard deviation was 5.7. Tests The Vocational Preference Inventory (VPI) (Holland, 1970) consists of a list of 160 occupations which when scored yield 11 scales (viz, Realistic, Intellectual, Artistic, Social, Enterprising, Conventional, Self-Control, Masculinity, Status, -Infrequency, and Acquiescence). An individual’s score on each of these scales is simply the number of corresponding occupations which he endorses. The first six of the scales represent personality types.
COMPARISON
OF HOLLAND’S
MODEL
247
In describing the personality types, Holland lists 13 to 16 adjectivesper type (Holland, 1973). The adjectives are believed to be descriptors of the respective personality types. There are, in all, 78 different adjectives used to describe the six types. An alphabetical list of the pool of 78 adjectiveswas constructed, each of the subjectswas provided with a list of the adjectivesand instructed to respond yes if the adjective was self-descriptive and no if the adjective was not consideredself-descriptive. Raw scoreswere obtained for each of the subjects on the adjective list by counting the number of adjectives marked yes for each of the six types. Nine of the adjectives occur on two type descriptions and were therefore scored on both. Holland (1970, 1973) proposes a hexagonal model of personality types which rotate clockwise around the hexagon in the following order, Realistic, Intellectual, Artistic, Social, Enterprising, and Conventional. In this study, if the two methods measured the same six constructs, the hexagon formed by the constructs measu.redby the WI (R, I, A, S, E, C) would lie in exactly the same place, in factor space, as the constructs measuredby the AL (R’, I’, A’, S’, E’ , C’) and the relationship would be that hypothesized by Holland. Procedure
The 11 scalesof the VP1 and the six scalesof the AL were analyzed by the principal components method (Harman, 1967). As a geometric structure involving 12 points, or 12 scales,was to be tested, a factor-spaceof at least 11 dimensions was necessary(Shepard 1962a, p. 128; 1962b, pp. 238-240). In order to obtain this space, the first 11 principal components were extracted. These principal components were rotated by Varimax. In the space defined by the first 11 principal components, distances between each of the first six scalesof the WI and each of the six AL scales were computed. If the VF’I scales and the AL scalesmeasurethe hexagonal arrangement of personality types (Holland, 1973) in a parallel fashion, a specific pattern of distances between the two sets of scalesshould be found. Four classesof distances may be derived from the double hexagonal geometric structure. There should be a set of six short distances connecting the Realistic scale of the VP1 with the Realistic scale of the AL, etc. There should be a set of 12 slightly longer distances, called short middle distances, that connect the Realistic scale of the VP1 with the Intellectual or the Conventional scale of the AL, etc. In other words, the short middle distances connect adjacent scalesacrossthe two instruments. A set of 12 slightly longer distances connect the alternate or two scales distant across the two instruments. An example of two of these distances,called the long middle distance, is the connection between the Realistic VI’1 scale and the Artistic AL scale or the connection between the Realistic VP1 scale and the Enterprising AL scale.
CC’
EE’
ss
AA
II’
RR’
< 72 comparisons (6x 12) 48 in the expected direction
Are less than RC’ RI IA’ II? AS’ AI’ SE’ SA’ ES’ EC’ CE’ CR’
Short middle distances
OA total of 288 comparisons was made.
Short distances RE’ RA’ IS’ IC’ AR’ AE’ SC’ SI’ ER’ EA’ cs CI’
Long middle distances
< 144 comparisons (12X12) 84 in the expected direction
Are less than
TABLE 1 Comparisons between Four Classes of Distancesa
< 72 comparisons (6X 12) 42 in the expected direction
Are less than
CA’
EI’
SR’
AC
IE’
RS ’
Long distances
COMPARISON OF HOLLAND’S MODEL
249
A set of six long distances should connect the opposite scales of the two instruments, for examples, the Realistic VP1 scalewith the Social AL scale or the Intellectual VP1 measureas opposed to the AL Enterprising measure. Comparing the short distanceswith the short middle distances,the short middle with the long middle distances, and the long middle with the long distances requires 288 comparisons as shown in Table 1 between two distances.Only adjacent classesof distancesare compared (e.g., short distances are compared only with short middle distances and not with long middle or long distances (see Table 1) in order to avoid non-independent comparisons. The reason that nonadjacent classesof distancesare not compared is that their outcome may be determined by the outcome of the comparison of adjacent classes.For example, if the short distance RR’ were comparedwith the short middle distance RC’ , and the outcome was correct, and the short middle distance RC’ was compared with the long middle distance RR’, and the outcome was also correct, then the comparison of RR’ and RE’ would necessarily be correct. That is, if RR’ is less than RC’ and RC’ is less than RE’, then RR’ must be less than RE’. Thus comparisons between nonadjacent classesare not made. Each distance comparison is judged either to correspond to its hypothesized direction or not to correspond to its hypothesized direction. A binomial test similar to that presented by Wakefield and Doughtie (1973) was computed to test for the overall correspondencebetween the hexagonal structures of the six WI scalesand the six AL scales. RESULTS AND DISCUSSION Of the 288 distance comparisons made, 174 were in the hypothesized direction as shown in Table 1. The normal approximation to the binomial test yielded a z of 3.477 (p < .Ol). This result supports the correspondence between the VP1 and AL scales. The significant correspondenceof the relationships between the two sets of constructs based on two different methods of measuring those constructs gives additional support to Holland’s model. It is evidence that the relationships posited by Holland’s theory are not tied to one particular method of measurement. This is to say that the relationships specified by Holland’s theory in the nomological network have some generality acrossmethods of measurementand are thus shown not to be tied to any one particular method of measurement. REFERENCES Campbell, D. T., & Fiske, D. W. Convergent and discriminant validation by the multitrait-multimethod matrix. Psychologicd Bulletin, 1959, 56, 81-105.
250
BOBELE ET AL.
Cole, N. S., Whitney, D. R., & Holland, J. L. A spatial configuration of occupations. Journal of Vocational Behavior, 1971, 1, l-9. Cronbach, L. J., & Meehl, P. E. Construct validity in psychological tests. Psychological Bulletin, 1955, 52, 281-302. Doughtie, E. B., Wakefield, J. A., Jr., Sampson, R. N., & Alston, H. L. A statistical test of the theoretical model for the representational level of the ITPA. Journal of Educational Psychology, 1974, 66, 410-415. Harman, H. H. Modern Factor Analysis. Chicago, Illinois: University of Chicago Press, 1967. Holland, J. L. Making vocational choices: A theory of careers. Englewood Cliffs, New Jersey: Prentice Hall, 1973. Holland, J. L. Manual for the Vocational Preference Inventory. Palo Alto, California: Consulting Psychologists Press, 1970. Shepard, R. N. The analysis of proximities: Multidimensional scaling with an unknown distance function. I. Psychometrica, 1962, 27, 125-140. (a) Shepard, R. N. The analysis of proximities: Multidimensional scaling with an unknown distance function. 11.Psychometrica, 1962, 27, 219-246. (.b) Waketield, J. A., Jr., & Doughtie, E. B. The geometric relationship between Holland’s personality typology and the Vocational Preference Inventory. Journal of Counseling Psychology, 1973, 20, 513-518. Wakefleld, J. A., Jr., Yom, B. L., Doughtie, E. B., Chang, W. C., & Alston, H. L. The geometric relationship between Holland’s personality typology and the Vocational Preference Inventory for blacks. Journal of Counseling Psychology, 1975, 3 58-60. Webb, E. J., Campbell, D. T., Schwartz, R. D., & Se&rest, L. Unobtrusive measures: Nonreactive research in the social sciences. Chicago, Illinois: Rand McNally, 1966. REFERENCE NOTE 1. Bobele, R. M., Alston, H. L., Wakefield, J. A., Jr., & Schnitzen, J. P. Relationships among personality types using constructs measured Holland’s theory. Unpublished manuscript, 1974.
Received: November 21, 1975.
by
adjectives
derived
from
of Vocational
Behavior 9, 245-250 (1976)
A Comparison of Holland’s Model Using Constructs Measured by Two Different Methods R. MONTE BOBELE North Harris County College HERBERT L. ALSTON University of Houston JAMES A. WAKEFIELD, JR. California State College, Stanislaus and EUGENE B. DOUGHTIE University of Houston
The relationship was studied between the set of constructs specified by Holland’s (1973) theory (viz, Realistic, InteIIectual, Artistic, Social, Enterprising, and Conventional) measured by an Adjective List (AL) derived from Holland’s theory and the same set of constructs as measured by the Vocational Preference Inventory (VPI). The correspondence of the two measures of Holland’s model compared the distances between the constructs as measured by the AL and the constructs measured by the VP1 in factor space using an adaptation of a model testing procedure reported by Wakefield and Doughtie (1973). The subjects were 174 undergraduates at a state university. The correspondence between the two separate measures of Holland’s model was significant @ < .Ol). These results provide further support of the construct validity of Holland’s theory and offer evidence that the relationships hypothesized by the theory are not tied to any one particular method of measurement.
Holland (1973) presented a theory of careers based on six personality types (viz, Realistic, Intellectual, Social, Conventional, Enterprising, and Artistic). The relationships among these types are specified by a hexagonal model, where the distances between the constructs in the model are hypothesized to correspond to psychologically meaningful distances. This is to say that the closer two constructs are in the model, the more similar individuals would be who correspond to these types. The relationships among the Requests for reprints should be sent to Dr. Eugene B. Doughtie, Department Psychology, University of Houston, 3801 Cullen Boulevard, Houston, TX 77004.
24.5 Copyright @ 1976 by Academic Press, Inc. All rights of reproduction in any form reserved.
of
246
BOBELE ET AL.
constructs in Holland’s model have received considerable support when those constructs were measured by the Vocational Preference Inventory (VPI) (HolIand, 1970) (cf. Cole, Whitney, & Holland, 1971; Wakefield & Doughtie, 1973; Wakefield, Yom, Doughtie, Chang, & Alston, 1974). A psychological construct is a hypothetical entity and is defined in terms of its relationship to other such constructs. Such a system of stated relationships among constructs constitutes a theory or a nomological network (Cronbach & Meehl, 1955). By definition, a construct is not synonymous with the operations by which it is measured and construct validity refers to empirical evidence for the postulated relationships among the constructs (Cronbach & Meehl, 1955). Several researchers have argued for the use of more than one method of measurement (Campbell & Fiske, 1959; Cronbach & Meehl, 1955; Webb, Campbell, Schwartz, & Sechrest, 1966) to validate a theory. To the extent that different methods of measurement of the constructs employed in a theory result in the relationships predicted by the theory, the theory is considered to be more firmly established and perhaps more general in its application. Bobele, Alston, Wakefield, and Schnitzen (1974) recently reported that Holland’s model was supported using the model testing procedure of Wakefield & Doughtie (1973); (cf. Doughtie, Wakefield, Sampson, & Alston, 1974) with constructs measured by an adjective list derived from Holland’s theory. The present study compares the relationships between the set of constructs measured by the adjective list and the same set of constructs measured by the VP1 using an adaptation of the aforementioned model testing procedure. METHOD Subjects One hundred and seventy-four students enrolled in undergraduate psychology courses at the University of Houston participated in the present study. The sample was comprised of 92 women (53%) and 82 men (47%). The mean age of the subjects was 23.7 yr and the standard deviation was 5.7. Tests The Vocational Preference Inventory (VPI) (Holland, 1970) consists of a list of 160 occupations which when scored yield 11 scales (viz, Realistic, Intellectual, Artistic, Social, Enterprising, Conventional, Self-Control, Masculinity, Status, -Infrequency, and Acquiescence). An individual’s score on each of these scales is simply the number of corresponding occupations which he endorses. The first six of the scales represent personality types.
COMPARISON
OF HOLLAND’S
MODEL
247
In describing the personality types, Holland lists 13 to 16 adjectivesper type (Holland, 1973). The adjectives are believed to be descriptors of the respective personality types. There are, in all, 78 different adjectives used to describe the six types. An alphabetical list of the pool of 78 adjectiveswas constructed, each of the subjectswas provided with a list of the adjectivesand instructed to respond yes if the adjective was self-descriptive and no if the adjective was not consideredself-descriptive. Raw scoreswere obtained for each of the subjects on the adjective list by counting the number of adjectives marked yes for each of the six types. Nine of the adjectives occur on two type descriptions and were therefore scored on both. Holland (1970, 1973) proposes a hexagonal model of personality types which rotate clockwise around the hexagon in the following order, Realistic, Intellectual, Artistic, Social, Enterprising, and Conventional. In this study, if the two methods measured the same six constructs, the hexagon formed by the constructs measu.redby the WI (R, I, A, S, E, C) would lie in exactly the same place, in factor space, as the constructs measuredby the AL (R’, I’, A’, S’, E’ , C’) and the relationship would be that hypothesized by Holland. Procedure
The 11 scalesof the VP1 and the six scalesof the AL were analyzed by the principal components method (Harman, 1967). As a geometric structure involving 12 points, or 12 scales,was to be tested, a factor-spaceof at least 11 dimensions was necessary(Shepard 1962a, p. 128; 1962b, pp. 238-240). In order to obtain this space, the first 11 principal components were extracted. These principal components were rotated by Varimax. In the space defined by the first 11 principal components, distances between each of the first six scalesof the WI and each of the six AL scales were computed. If the VF’I scales and the AL scalesmeasurethe hexagonal arrangement of personality types (Holland, 1973) in a parallel fashion, a specific pattern of distances between the two sets of scalesshould be found. Four classesof distances may be derived from the double hexagonal geometric structure. There should be a set of six short distances connecting the Realistic scale of the VP1 with the Realistic scale of the AL, etc. There should be a set of 12 slightly longer distances, called short middle distances, that connect the Realistic scale of the VP1 with the Intellectual or the Conventional scale of the AL, etc. In other words, the short middle distances connect adjacent scalesacrossthe two instruments. A set of 12 slightly longer distances connect the alternate or two scales distant across the two instruments. An example of two of these distances,called the long middle distance, is the connection between the Realistic VI’1 scale and the Artistic AL scale or the connection between the Realistic VP1 scale and the Enterprising AL scale.
CC’
EE’
ss
AA
II’
RR’
< 72 comparisons (6x 12) 48 in the expected direction
Are less than RC’ RI IA’ II? AS’ AI’ SE’ SA’ ES’ EC’ CE’ CR’
Short middle distances
OA total of 288 comparisons was made.
Short distances RE’ RA’ IS’ IC’ AR’ AE’ SC’ SI’ ER’ EA’ cs CI’
Long middle distances
< 144 comparisons (12X12) 84 in the expected direction
Are less than
TABLE 1 Comparisons between Four Classes of Distancesa
< 72 comparisons (6X 12) 42 in the expected direction
Are less than
CA’
EI’
SR’
AC
IE’
RS ’
Long distances
COMPARISON OF HOLLAND’S MODEL
249
A set of six long distances should connect the opposite scales of the two instruments, for examples, the Realistic VP1 scalewith the Social AL scale or the Intellectual VP1 measureas opposed to the AL Enterprising measure. Comparing the short distanceswith the short middle distances,the short middle with the long middle distances, and the long middle with the long distances requires 288 comparisons as shown in Table 1 between two distances.Only adjacent classesof distancesare compared (e.g., short distances are compared only with short middle distances and not with long middle or long distances (see Table 1) in order to avoid non-independent comparisons. The reason that nonadjacent classesof distancesare not compared is that their outcome may be determined by the outcome of the comparison of adjacent classes.For example, if the short distance RR’ were comparedwith the short middle distance RC’ , and the outcome was correct, and the short middle distance RC’ was compared with the long middle distance RR’, and the outcome was also correct, then the comparison of RR’ and RE’ would necessarily be correct. That is, if RR’ is less than RC’ and RC’ is less than RE’, then RR’ must be less than RE’. Thus comparisons between nonadjacent classesare not made. Each distance comparison is judged either to correspond to its hypothesized direction or not to correspond to its hypothesized direction. A binomial test similar to that presented by Wakefield and Doughtie (1973) was computed to test for the overall correspondencebetween the hexagonal structures of the six WI scalesand the six AL scales. RESULTS AND DISCUSSION Of the 288 distance comparisons made, 174 were in the hypothesized direction as shown in Table 1. The normal approximation to the binomial test yielded a z of 3.477 (p < .Ol). This result supports the correspondence between the VP1 and AL scales. The significant correspondenceof the relationships between the two sets of constructs based on two different methods of measuring those constructs gives additional support to Holland’s model. It is evidence that the relationships posited by Holland’s theory are not tied to one particular method of measurement. This is to say that the relationships specified by Holland’s theory in the nomological network have some generality acrossmethods of measurementand are thus shown not to be tied to any one particular method of measurement. REFERENCES Campbell, D. T., & Fiske, D. W. Convergent and discriminant validation by the multitrait-multimethod matrix. Psychologicd Bulletin, 1959, 56, 81-105.
250
BOBELE ET AL.
Cole, N. S., Whitney, D. R., & Holland, J. L. A spatial configuration of occupations. Journal of Vocational Behavior, 1971, 1, l-9. Cronbach, L. J., & Meehl, P. E. Construct validity in psychological tests. Psychological Bulletin, 1955, 52, 281-302. Doughtie, E. B., Wakefield, J. A., Jr., Sampson, R. N., & Alston, H. L. A statistical test of the theoretical model for the representational level of the ITPA. Journal of Educational Psychology, 1974, 66, 410-415. Harman, H. H. Modern Factor Analysis. Chicago, Illinois: University of Chicago Press, 1967. Holland, J. L. Making vocational choices: A theory of careers. Englewood Cliffs, New Jersey: Prentice Hall, 1973. Holland, J. L. Manual for the Vocational Preference Inventory. Palo Alto, California: Consulting Psychologists Press, 1970. Shepard, R. N. The analysis of proximities: Multidimensional scaling with an unknown distance function. I. Psychometrica, 1962, 27, 125-140. (a) Shepard, R. N. The analysis of proximities: Multidimensional scaling with an unknown distance function. 11.Psychometrica, 1962, 27, 219-246. (.b) Waketield, J. A., Jr., & Doughtie, E. B. The geometric relationship between Holland’s personality typology and the Vocational Preference Inventory. Journal of Counseling Psychology, 1973, 20, 513-518. Wakefleld, J. A., Jr., Yom, B. L., Doughtie, E. B., Chang, W. C., & Alston, H. L. The geometric relationship between Holland’s personality typology and the Vocational Preference Inventory for blacks. Journal of Counseling Psychology, 1975, 3 58-60. Webb, E. J., Campbell, D. T., Schwartz, R. D., & Se&rest, L. Unobtrusive measures: Nonreactive research in the social sciences. Chicago, Illinois: Rand McNally, 1966. REFERENCE NOTE 1. Bobele, R. M., Alston, H. L., Wakefield, J. A., Jr., & Schnitzen, J. P. Relationships among personality types using constructs measured Holland’s theory. Unpublished manuscript, 1974.
Received: November 21, 1975.
by
adjectives
derived
from