Partially random MMPI-2 protocols: When are they interpretable?

In clinical practice, the second edition of the Minnesota Multiphasic Personality Inventory (MMPI-P) validity indices are used to identify and subsequently exclude from interpretation protocols that include random responding. However, given that the items that comprise the clinical scales all fall within the first 370 items of the MMPI-2, if the onset of random responding occurs after item 370, then the clinical scales may be interpretable. The present report examines the utility of the standard and alternative MMPI-2 validity indices for detecting random responding within the first 370 items. Results suggested that all validity indices studied differed significantly between Interpretable and Uninterpretable protocols; however the Infrequency scale (F), the alter-native index F + Fb + \F - Fb\, and the Blocked Infrequency index (the number of 100 item MMPI-2 blocks with significant endorsements of F and Fb items equal to or exceeding 27%) provided for the highest hit rates across examined base rates of random responding. In addition, the proposed Variable Response Inconsistency-Front index (VRINf) also provided for highly accurate classification rates and had specific advantages, including the scale's probable insensitivity to overreporting. Despite the promising nature of these findings, caution is encouraged in using MMPI-2 validity scales in this manner until these findings are cross-validated.