The Utility of K-Correction to Adjust for a Defensive Response Set on the MMPI

Abstract

This study examined the utility of the K-correction procedure to adjust for a defensive response set on the MMPI. The sample consisted of 61 patients with end-stage lung disease undergoing psychosocial evaluation for transplantation. Participants were separated into "defensive" and "non-defensive" groups using a median split on the K scale (defensive group T score? 59) as the cutoff score. The MMPI was scored once in the standard manner and then rescored omitting all K-scale items from the clinical scales. As hypothesized, raw score analysis after omitting K-scale items showed the defensive group endorsed significantly fewer items on all five scales involving K-correction (Scales Hs, Pd, Pt, SC, Ma). Analysis of K-corrected T scores on Scales Hs, Pd, Pt, and Sc using standard procedures showed a significant group difference only on Scale Hs with a higher T score found among the defensive group. The defensive and nondefensive groups were not significantly different in demographic, medical, or psychiatric characteristics suggesting that the tendency to respond in a defensive manner is the major characteristic that distinguishes the two groups. Taken together, these results provide support for the use of the K-correction procedure when examining MMPI clinical profiles among patients with endstage pulmonary disease undergoing evaluation for transplantation.