Effective Cutoffs for Detecting Random, Partially Random, and Nonrandom 370-Item MMPI–2 Short Form Protocols

Abstract

The ability of the 370-item short form MMPI–2 (Butcher, Graham, Ben-Porath, Tellegen, Dahlstrom, & Kaemmer, 2001) validity scales to detect random protocols was investigated using samples of 500 nonrandom protocols, 250 half-random protocols, and 250 all-random protocols. The long-form cutoff of VRIN ⩾ 80 was unable to detect protocols with either level of randomness. The long-form cutoffs of Fp ⩾ 100 or F ⩾ 100 were able to detect all-random but not half-random protocols. Alternative cutoffs for VRIN, Fp, and F were investigated and short-form subscales of those scales were developed to improve detection of partially random protocols. An algorithm using alternative cutoffs for the scales and the new subscales was highly effective, detecting almost all of the random protocols as well as the nonrandom protocols. A follow-up cross-validation study was conducted that confirmed the effectiveness of the algorithm.

Notes

¹Weighted base rate data were calculated by multiplying the cell sizes for the nonrandom participants by a factor of [RD × (1/BR—1)] / NR, where BR is the base rate, RD is the number of random protocols, and NR is the number of nonrandom protocols.