An Empirical Occupational Classification Derived from a Theory of Personality and Inteded for Practice and Research

ACT RESEARCH REPORTNo. 2929April, 1969AN EMPIRICAL OCCUPATIONAL CLASSIFICATION DERIVED FROM A THEORY OF PERSONALITY AND INTENDED FOR PRACTICE AND RESEARCHJohn L. Holland Douglas R. Whitney Nancy S. Cole James M. Richards, Jr.American C o lle g e T e s t i n g ProgramP . 0 . Box 16 8 , Iowa C i t y , Iowa 52240 Summa ryThe origin, development, verification, and revision of an occupational classification is presented. The classification organizes occupations according to their degree of psychological "relatedness" following Holland's theory of personality. Because of its theoretical simplicity and empirical base, the classification has many potential practical applications for vocational guidance, industrial personnel work, and research in education, psychology, and sociology. An Empirical Occupational Classification Derived from a Theoryof Personality and Intended for Practice and ResearchJohn L. Holland, Douglas R. Whitney, Nancy S. Cole James M. Richards, Jr.^This report presents a revision of the occupational classification scheme first proposed and tested in an earlier study (Holland, 1966b).The many desirable features of this revised classification enhance its potential value both for research and for vocational guidance and personnel work.The Original ClassificationIn 1959, Holland proposed an a priori occupational classification of six categories. From 1959 to 1965, this classification was used in several theoretical studies, but it was neither directly tested for its value as a classification system nor explicitly defined for clear and easy use. Later Holland (1966b) defined the major categories of the clas sif ication --Realistic, Intellectual, Artistic, Social, Enterprising, and Conventional--in terms of the six Vocational Preference Inventory (VPI) scales having the same names. The assumption that occupational titles in the VPI scales define comparable categories in the classification made an explicit reconstruction of the classification possible.To obtain the first empirical version of the classification (Holland, 1966a), a profile of VPI means was calculated for students planning to enter each occupation. An occupation’s coded profile (highest scale mean first, next highest scale second, etc. ) defined an occupation's place in the classification. For example, an occupation with a code of RIES was placed in the major catego ry - -R eal istic.The remainder of the code indicated that occupation's particular subgroup within its major category. The application of this procedure to the VPI data for 12,432 college freshmen in 31 institutions (Abe et al, 1965) produced separate classifications for men and women.The classification for men included all six major VPI categories (R eal istic, Intellectual, Artistic, Social, Enterprising, and Conventional), each with one or more subgroups. The VPI data for women yielded only four major groups (Intellectual, Artistic,Social, Conventional) with a number of subgroups within each of the major categories.This first classification was tested for its usefulness in a series of studies. In the first study, Holland (1966a) obtained several favorable results: the classification developed from one -2-sample (N=12,432 college students) produced expected results when applied to another sample (N=10, 646 college students). When students were grouped into six categories according to their occupational choice, their highest mean score occurred on the corresponding VPI scale; that is, students who chose occupations previously classified as "Realistic'1 had the Realistic scale of the VPI as their highest mean score. Also, their mean on that scale was higher than the Realistic mean of any other occupational group. Without exception, similar findings held for the remaining occupational groups of men and women.In a second study, Holland (1968b) demonstrated that individual profiles using one, tw>o, and three scales could be interpreted according to his theory of personality types. For example, Realistic peaks were associated with technical competencies and mechanical ability; Intel­lectual peaks were associated with scientific competencies, mathematical ability, etc. Students with the same high point scale can still be distinguished by their second highest VPI scale. And students whose first two highest scales were the same, can still be distinguished by their third highest scale. For these three levels of predictive difficulty, 64-84% of the theoretical predictions of peaks for students with different characteristics wer