Using estimated factor scores from a bifactor analysis to examine the unique effects of the latent variables measured by the WAIS-IV on academic achievement.

This study used estimated factor scores from a bifactor analysis of the Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV) to examine the unique effects of its latent variables on academic achievement. In doing so, we addressed the potential limitation of multicollinearity in previous studies of the incremental validity of the WAIS-IV. First, factor scores representing psychometric g and 4 group factors representing the WAIS-IV index scales were computed from a bifactor model. Subtest and composite scores for the Wechsler Individual Achievement Test-Third Edition (WIAT-II) were then predicted from these estimated factor scores in simultaneous multiple regression. Results of this study only partially replicated the findings of previous research on the incremental validity of scores that can be derived from performance on the WAIS-IV. Although we found that psychometric g is the most important underlying construct measured by the WAIS-IV for the prediction of academic achievement in general, results indicated that the unique effect of Verbal Comprehension is also important for predicting achievement in reading, spelling, and oral communication skills. Based on these results, measures of both psychometric g and Verbal Comprehension could be cautiously interpreted when considering high school students' performance in these areas of achievement.