Two methods for studying the incremental validity of a Rorschach variable.

Abstract

The MMPI can be scored by a clerk. Also, both the number and form level of Rorschach responses can be easily assessed. Other Rorschach variables should be examined for their incremental validity beyond number of responses and form level, or from these variables plus simple MMPI variables. This study applied multiple regression analyses to 2 data sets with reasonable criteria of pathology that were predicted by W. Perry and D. J. Viglione's (1991) Ego Impairment Index considered alone. The index had only slight incremental validity over and above the number of responses and form quality, and even less when the average MMPI elevation and L. R. Goldberg's (1965) formula for predicting psychosis versus neurosis were entered before these Rorschach variables. Another way of assessing incremental validity is through the use of unit weights, that is, adding standardized variables weighted equally rather than optimally. The unit-weighted incremental validity analysis resulted in the same conclusions.