Interpreting low Personality Psychopathology-Five Aggressiveness scores on the MMPI-2: Graphical, robust, and resistant data analysis.

The Minnesota Mutiphasic Personality Inventory-2 (MMPI-2)-based Personality Psychopathology-Five (PSY-5) scales provide an overview of personality individual differences. Several textbooks and a test report offer instruction on interpreting MMPI-2 PSY-5 scores. On the basis of an earlier item response theory article (S. V. Rouse, M. S. Finger, & J. N. Butcher, 1999), low scores on the PSY-5 Aggressiveness (AGGR) scale are not currently interpreted. Traditional statistical methods are supplemented with graphical, robust, and resistant methods in the study of 188 outpatient men and 287 outpatient women. With locally weighted regression smoothing, the AGGR scale appeared to bear approximately linear relationships to scales formed from therapist ratings of patients. Pearson correlations tested by t test for significance showed correspondence with robust bootstrapped tests. Low-cut subsamples of men and women at or below the 33rd normative percentile showed that resistant correlations with robust tests showed moderate convergence with traditional methods. Results clearly suggested that low AGGR scores on the PSY-5 should be interpreted as suggesting low aggressiveness and passive and submissive features. Resistant and robust analyses suggest that gradations of aggressiveness, even within a low AGGR score group, can be interpreted. (PsycINFO Database Record (c) 2010 APA, all rights reserved)