Analysis of MMPI Data for Classification Purposes by Multivariate Statistical Techniques
THE PURPOSE of this paper is to present the steps involved in the appl i cation of multivariate analysis to the assignment?with a minimum error of classification?of Npeople to q criterion groups on the basis of all information provided by k in tercorrelated measures. The study itself stems from the writer's at tempt to identify as potential delinquents or non delinquents (q = 2), a population of ninth-grade high-school boys (N= 1802) to whom the MMPI had been administered by Hathaway (3) in 1947-1948, and for whom police and/or court records were available through 1952. Severity of misdemeanor made possible a classification of delinquency into eight levels. Because of i n t e r-group similarity of MMPI profiles between nondelinquents and de linquents atlevelsoneandtwo, the latter (N = 363) have been omitted from this study (see Table I). Variables used in one part of the study, re ferred to as the main study, consisted of the scores on the F, Hs, Sc, Mf, andPd scales of the MMPI (k = 5); in another part, the school study, they consisted of the Ma, Sc, Mf, and Pd scales of the MMPI; honor point ratio, and numbers of days absent in Grade VIII (k = 6). In the main study the MMPI profiles of 351 boys who had achieved delinquency status by 1952 were divided by random procedures into two groups: Sample A (N = 175) which was used in the develop ment of the classification formula, and Sample B (N=176), set aside for cross-validation pur poses. Two samples of 175 profiles each were similarly selected from the nondelinquent set of MMPI profiles. In t h e s c hool study both delin quent and nondelinquent groups were divided in to Samples Af and B* and four sub-groups (N = 91) were thus similarly obtained.