Evaluating Discrepancy Analyses With the Wisc-Iii and Wiat

Abstract

Multiple regression was used to examine the predictive power of the four index scores of the Wechsler Intelligence Scale for Children-Third Edition (WISGIII; Wechsler, 1991) in forecast ing student achievement ( N = 300) as mea sured by the Wechsler Individual Achievement Test (WIAT; The Psychological Corporation, 1992). Separate equations were developed for each of the WIAT's composite scores (i.e., Total, Reading, Mathematics, Language, and Writing) using a forward-entry procedure. WISC-III index scores not found to contribute a significant amount of variance to each equa tion were removed. The stability of the result ing reduced equations was supported through cross-validation with an independent sample ( N= 208). Results indicate that the WISC-III's index scores provide better prediction of WIAT achievement composites than does the FSIQ and yield smaller standard errors of estimate. Separate equations are provided for predicting expected achievements for each of the WIAT composite scores.