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

Abstract

MMPI-2 standardization data were re-sampled using Monte Carlo simulations to estimate the base rate of apparently abnormal scores expected by chance in the normal population when multiple scales are interpreted. 36.8% of normal adults are likely to obtain a score that would otherwise be considered clinically significant at 65T on one or more of the 10 Clinical scales. The normal incidence of at least one apparently abnormal score was 38.3% on the Content and 55.1% on the Supplementary scales. When the Clinical, Supplementary, and Content scales and subscales are interpreted together, at least three seemingly meaningful scores will be found in 47.4% of perfectly normal individuals, and five or more scales that appear to be clinically significant can be expected in 30.1% of cases that are actually unremarkable. These results imply that the number of MMPI-2 scales that can be meaningfully interpreted in clinical practice is limited, and that high T-scores are necessary for an adequate level of confidence even when interpretation is appropriately limited to the Clinical scales.