Incremental validity of MMPI and MMPI-2 clinical scales in detecting malingering

The efficacy of the F scale and F-K index in detecting faking of a mental illness was investigated for both the MMPI and MMPI-2. A total of 72 undergraduate students completed the MMPI and 74 completed the MMPI-2 after receiving instructions to feign severe mental illness. Student responses were analyzed against MMPI (n=180) and MMPI-2 (n=76) data obtained from psychiatric inpatients diagnosed with severe mental illnesses. Multiple regression analysis of the validity scales and F-K index indicate that the F scale is the best predictor of malingering both for the MMPI (r=64) and MMPI-2 (r=.74) and the two samples combined (r=.71). The Si and D scales accounted for statistically significant, yet small, amounts of incremental validity. The presence of a “sawtooth” pattern did not add any incremental validity. Though an F scale cut-off score of T>109 resulted in an 85.9% classification accuracy rate, it appears that categorizing scores into one of five ranges results in better classification accuracy than a single cut-off score.