Inconsistency Index for the Zuckerman-Kuhlman-Aluja Personality Questionnaire (ZKA-PQ)

The purpose of this study is the development of an index to assess inconsistency in the answers of Zuckerman-Kuhlman-Aluja Personality Questionnaire (ZKA-PQ) in order to identify and discard inconsistent subjects in applied psychology, as clinical, forensics, or personnel selection. The procedure consists in the use of 10 pairs of highly correlated items in a wide sample of voluntary and anonymous subjects of both sexes (n = 5.644). We inserted random cases to the original data in order to obtain simulated scores of inconsistency and we established a cut-off criterion to discriminate between consistent and inconsistent subjects according to a 70 T Score. A score higher than 10 points discriminated the 3.7% of the subjects. Cronbach's alpha average for facets was calculated by ZKA-PQ facets distributed in 8 (alpha: 0.79), 9-10 (alpha: 0.67), and above 10 points (alpha:.50) of the inconsistency index. The Feldt test indicates that alpha differences were significant. The inconsistency score did not affect the factorial structure of the ZKA-PQ. We discussed the utility of this index to identify inconsistent subjects with the ZKA-PQ, as, for instance, those with individual difficulties (a limited vocabulary, poor verbal comprehension, an idiosyncratic way of interpreting item meanings, carelessness, inattentiveness...).