MMPI-2 clinical scales and 2-point code types: Impact of varying levels of omitted items

The study investigated the impact of varying levels of item omissions (Cannot Say) on Minnesota Multiphasic Personality Inventory-2 (MMPI-2) 2-point code types. Valid MMPI-2 answer sheets were obtained from psychological outpatients (N = 100). Seven levels of item omission were investigated: 0 (baseline), 5, 10, 15, 20, 25, and 30. Omitted items were those most frequently skipped by psychiatric outpatients. Statistically reliable but very slight declines were seen on MMPI-2 clinical scales (M = -1.8 T-score points at 30 Cannot Says). Defined 2-point code types were relatively stable in the face of up to 30 omitted items. However, undefined code types were changed in 25% of the cases by 10 omitted items and in 39% of the cases by 30 omitted items. These results suggest that defined code types are relatively robust in the face of up to 30 omitted items, although undefined code types appeared much more likely to be changed by omitted items even at low levels. It is recommended that item content always be reviewed in the presence of omitted items to determine if specific clinical or content scales might be affected.