Rates of Apparently Abnormal MMPI-2 Profiles in the Normal Population

• Main Author: Odland, Anthony Paul
• Format: Others
• Published: NSUWorks 2013
• Subjects: Base rates; Minnesota Multiphasic Personality Inventory; Psychometrics; Psychopathology; Psychology
• Online Access: http://nsuworks.nova.edu/cps_stuetd/57; http://nsuworks.nova.edu/cgi/viewcontent.cgi?article=1056&context=cps_stuetd

Previous research suggests as more scores are interpreted, there is a coinciding increase in the chance significant scores will be obtained. Interpretation of the MMPI-2 can involve the analysis of as many as 98 or more separate scores, suggesting the measure has a strong proclivity for producing a high frequency of seemingly abnormal scores amongst normal healthy adults. In the current study the incidence of elevated MMPI-2 scores was simulated for the normal population using Monte Carlo methodology. Interscale correlations from the MMPI-2 restandardization sample were obtained to determine the percentage of the population with N or more seemingly abnormal scores. Simulations were conducted for all scales combined, and for the Clinical, Harris-Lingoes, Content, Content-Component, and Supplementary scales separately at varying T-score cutoffs. 36.8% of normal adults are expected exhibit at least one elevated score on the Clinical scales at 65T. The normal incidence of at least one seemingly abnormal score was 38.3% on the Content, and 55.1% on the Supplementary scales. When all scale groups are considered together, approximately 50% of the normal population has three or more significant scores, and at least seven seemingly meaningful scores are found for one out of five normal persons. These results imply that consideration of a large number of MMPI-2 scales should be conducted with caution, and that high T-score cut-points may optimally increase confidence in the absence of corroborative test scores and extra test data.