Empirically derived ability-achievement subtypes in a clinical sample.

The purpose of the present study was to identify reliable and clinically meaningful patterns of ability and achievement using the WISC-III and WIAT. Cluster analysis was used to group the 182 WISC-III and WIAT profiles (10 WISC-III subtests and 4 WIAT subtests) of children between the ages of 9 and 14 years. Theoretical and empirical considerations were used to identify a cluster solution, which involved comparison of several five-, six- and eight-cluster solutions. A five-cluster solution was selected as being representative of the data, which was well replicated across three hierarchical clustering methods (i.e., complete linkage, average linkage-within groups, and average linkage-between groups (UPGMA)). The clusters were labeled based on their most salient characteristics, which included a group of predominantly low ability and achievement, a group demonstrating a pattern of verbal processing deficits, a group demonstrating a pattern of visual spatial/processing speed deficits, a group with low ability and achievement with average processing speed, and a group with deficits consistent with an ACID pattern. The external validity of the five subtypes was assessed through an evaluation of the relationship between cluster membership and neuropsychological test data. Most predictions regarding neuropsychological performance were supported by the data, providing further evidence of the validity of the five-cluster solution. Clinical implications of the ability-achievement typology and suggestions for future research are discussed.