Examining the Psychometric Equivalency of MMPI-3 Scale Scores Derived From the MMPI-3 and the MMPI-2-RF-EX

The current study evaluated the comparability of Minnesota Multiphasic Personality Inventory-3 (MMPI-3) scale scores derived from the 335-item MMPI-3 to MMPI-3 scale scores derived from the 433-item MMPI-2 restructured form-expanded version (MMPI-2-RF-EX), an enhanced version of the MMPI-2-RF that was used to develop and validate the MMPI-3. To that end, we examined data from 192 college undergraduates who completed both the MMPI-3 and MMPI-2-RF-EX 1 week apart using a counterbalanced design. Across versions, mean T-scores and standard deviations, estimates of internal consistency, and standard error of measurement values, were highly similar, indicating no clinically meaningful differences across versions. We also compared between-version test-retest comparability values with within-version values calculated using a sample of undergraduates (N = 318) who completed the MMPI-2-RF-EX twice over the same time interval, finding only marginal differences across the two samples. Finally, we computed column-vector correlations between MMPI-3 scores from both versions and several criterion measures, where results reflected no effect of test version on external validity. Overall, we determined that scale scores derived from either booklet are psychometrically interchangeable, indicating that MMPI-3 scale scores obtained from an administration of the MMPI-2-RF-EX can be applied when using the 335-item MMPI-3.