Date of Award


Publication Type

Doctoral Thesis

Degree Name





Dr. Joseph Casey




The purpose of this investigation was to determine the extent to which reliable and valid WISC-IV subtest patterns, consistent with those identified in taxonomic research using previous WISC editions, could be empirically derived in a sample of children referred for psychoeducational assessment. Two cluster analytic studies were conducted. In the first study, only the ten core subtests were used to form clusters. In the second study, ten core plus three supplemental subtests (i.e., Information, Picture Completion, and Arithmetic) were used to derive clusters. Through two-stage cluster analyses employing Ward's hierarchical method followed by k-means iterative partitioning analyses, virtually the same three clusters emerged in both studies. These clusters were characterized by (1) low scores on all subtests; (2) low scores on subtests associated with the VCI; and (3) low scores on subtests associated with the WMI and PSI. These clusters were internally valid in the sense that they remained stable across first and second stages of the initial cluster analysis, were derived using four distinct clustering algorithms, and were well-replicated across various samples. The Globally Low cluster identified in Study 1 differed from the other two clusters on three WIAT-II subtests. The external validity of the other clusters remains unclear. As hypothesized, the clusters derived in this investigation have been identified in taxonomic research using previous WISC editions. Unexpectedly, clusters characterized by poor performance on subtests historically associated with the VIQ and PIQ did not emerge, nor did clusters suggesting weaknesses in perceptual reasoning (i.e., PRI), visual processing (i.e., Gv), or nonverbal fluid reasoning (G f). Curiously, the Picture Concepts subtest represented the highest score in every cluster, failing to vary in a predictable manner with the other PRI subtests. Theoretical and clinical implications of this investigation are discussed and suggestions for future research are provided.