Core Profile Types for the WISC-III and WIAT: Their Development and Application in Identifying Multivariate IQ-Achievement Discrepancies

Abstract

This study sought to identify the most representative ability and achievement profiles for the Linking sample (N = 824) of the Wechsler Intelligence Scale for Children-Third Edition (WISC-III; Wechsler, 1991 and the Wechsler Individual Achievement Test (WIAT; Wechsler, 1992). The primary benefit of such a core profile typology is that it provides contrasts for testing multivariate IQ-achievement discrepancies. The typology was constructed using factor indexes from the WISC-III (Verbal Comprehension, Perceptual Organization, Freedom from Distractibility, Processing Speed) and Composite scores from the WIAT (Reading, Mathematics, Language, Writing). Scores from the WISC-III and WIAT were sorted according to shape, level, and dispersion using a three-stage clustering procedure that began with three separate agglomerative algorithms and iterated the results from each. The iterated Ward's solution best met all formal heuristic and statistical criteria. The resultant six core profile types are described according to population prevalence, score configuration, overall ability and achievement levels, and trends for parent and child demography. Thereafter, two methods are presented for determining multivariate IQ-achievement discrepancies. Whereas the first is mathematically precise, the second is more convenient to every day practice. A step-by-step worksheet is provided for the “everyday” method and a case study is analyzed using this procedure.