Evaluating discrepancy analyses with the WISC-III and WIAT

Multiple regression was used to examine the predictive power of the four in dex scores of the Wechsler Intelligence Scale for Children-Third Edition (W ISC-III; Wechsler, 1991) in forecasting student achievement (N = 300) as me asured 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 Writi ng) using a forward-entry procedure. WISC-III index scores not found to con tribute a significant amount of variance to each equation were removed. The stability of the resulting reduced equations was supported through cross-v alidation with an independent sample (N = 208). Results indicate that the W ISC-III's index scores provide better prediction of WIAT achievement compos ites than does the FSIQ and yield smaller standard errors of estimate. Sepa rate equations are provided for predicting expected achievements for each o f the WIAT composite scores.