Development and effects of an MMPI--A K-correction procedure

Although the results of research on the effectiveness of the K-correction factor have been inconclusive, this procedure has been widely used with adult respondents to correct for defensiveness or underreporting of symptomatology on the Minnesota Multiphasic Personality Inventory. Although the K-correction procedure was incorporated into the Minnesota Multiphasic Personality Inventory-2, the Minnesota Multiphasic Personality Inventory-Adolescent (MMPI-A) was developed based exclusively on the use of non-K-corrected T scores. This study derived age-appropriate K-weights for the MMPI-A to determine the degree to which the use of this procedure could improve test accuracy in the classification of participants into normal and clinical groups. Discriminant function analyses were performed to determine the K-weight that, when combined with basic scale raw score values, optimally predicted normal versus clinical status for each of the eight basic clinical scales. Hit rate analyses were utilised to assess the degree to which K-corrected T scores resulted in improvements in classification accuracy in contrast to standard MMPI-A non K-corrected norms. Results indicate that the adoption of K-correction procedure for the MMPI-A does not result in systematic improvements in test accuracy and the current findings do not support the clinical use of a K-correction factor in interpreting MMPI-A protocols.