The function computes seven differentiation indices for Holland profiles as cited in Bergman (1993) and Eder (1998).
dif_7_holland(A, ind = c("DI1", "DI2", "DI3", "DI4", "DI5", "DI6", "DI7"))a numeric vector with Holland score values for the interest profile of length = 6.
a character indicating which index (see table 1) to return.
a numeric with value for differentiation.
The function finds seven different (see argument ind) differentiation indices as cited Bergman (1993) and Eder (1998) for the Holland-interest profile given in argument A, which is the person interest profile consisting of six values (either raw scores or norms) for each of the six dimensions of vocational interests.
specific information on the indices of differentiation:
Table 1: Differentiation indices for Holland profiles. Source: Bergmann, (1993, p. 267).
| Index | Brief description | Author / Source |
| DI1 | Difference between highest and second highest interest score | (Frantz & Walsh, 1972) |
| DI2 | Difference between highest and third highest interest score | (Spokane & Walsh, I978) |
| DI3 | Difference between highest score and the average of the second and fourth highest score | (Iachan, 1984) |
| DI4 | Difference between highest score and the average of the third and fifth highest score | (Iachan, 1984) |
| DI5 | Difference between highest and lowest score | (Holland, 1973) |
| DI6 | Difference between highest and lowest score, standardized by the overall level of interest | (Peiser & Meir,1978) |
| DI7 | Dispersion of interest scores | (Healy & Mourton, 1983) |
Holland, J.L. 1963. A theory of vocational choice. I. Vocational images and choice. Vocational Guidance Quarterly, 11(4), 232<U+2013>239.
Bergmann, C. (1993). Differenziertheit der Interessen und berufliche Entwicklung. Zeitschrift f<U+00FC>r Differentielle und Diagnostische Psychologie, 14(4), 265<U+2013>279.
Frantz, T. T. & Walsh, E. P. (1972). Exploration of Holland's theory of vocational choice in graduate school environments. Journal of Vocational Behaviour, 2, 223-232.
Spokane, A. R. & Walsh, W. B. (1978). Occupational level and Holland's theory for employed men and women. Journal of Vocational Behaviour, 12, 145-154.
Iachan, R. (1984). A family of differentiation indices. Psychometrika, 49, 217-222.
Holland, J. L. (1973). Making vocational choices. Englewood Cliffs, New Jersey: Prentice Hall Inc.
Peiser, C. & Meir, E. I. ( 1978). Congruency, consistency, and differentiation of vocational interests as predictors of vocational satisfaction and preference stability. Journal of Vocational Behaviour, 12, 270-278.
Healy, C. C. & Mourton, D. L. (1983). Derivatives of the Self-Directed Search: Potential clinical and evaluative uses. Journal of Vocational Behavior, 23(3), 318<U+2013>328. https://doi.org/10.1016/0001-8791(83)90045-3
Eder, F. (1998). Differenziertheit der Interessen als Pr<U+00E4>diktor der Interessenentwicklung. In J. Abel & C. Tarnai (Hrsg.), P<U+00E4>dagogisch-psychologische Interessenforschung in Studium und Beruf (S. 63<U+2013>77). M<U+00FC>nster: Waxmann.
# NOT RUN {
# fictional interest profile:
A <- c(70, 90, 120, 75, 100, 130)
names(A) <- c("R","I","A","S","E","C")
# differentiation according to Frantz & Walsh (1972)
dif_7_holland(A, ind = "DI1")
# all of the differentiation indices
ind <- c("DI1","DI2","DI3","DI4","DI5","DI6","DI7")
sapply(ind, function(x)dif_7_holland(A,x),USE.NAMES = FALSE)
# }
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