Prorating Incomplete Wiggins and MacAndrew Scales

Abstract

A table is provided for prorating the Wiggins Content Scales and MacAndrew Alcoholism Scale from the Minnesota Multiphasic Personality Inventory (MMPI) when the entire form has not been completed. Conversion factors are given in increments of 10 items for 200 to 400 completed questions. Means, standard deviations, and comparisons of the number of scales over 70 were calculated from 236 profiles, using 200, 250, 300, 350, and 400 items. Results indicate that the conversion factors tend to overestimate scale elevations for the Wiggins scale. The MacAndrew scale can be used for clinical purposes with as few as 200 MMPI items completed, but clinical interpretation of prorated Wiggins scales should be done cautiously.