Empirically derived ability-achievement subtypes in a heterogeneous clinic-referred sample.

The purpose of the present study was to identify clinically meaningful and reliable patterns of ability and achievement using the WISC-III and WIAT. As an extension of the work of Saunders, Casey, and Jones (2001), it was anticipated that several of the derived subtypes would share a similar profile to many of the subtypes described in their research, and that many of the derived subtypes would demonstrate a predictable pattern of neuropsychological test results. 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. Ultimately, 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, and a group with deficits consistent with an ACID pattern. Three of the subtypes were found to be highly similar to subtypes of Saunders et al., and all five subtypes had been identified in the learning disabilities literature. The external validity of the five subtypes was assessed through evaluation of the relationship between cluster membership and neuropsychological profile. 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.Dept. of Psychology. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2004 .W39. Source: Dissertation Abstracts International, Volume: 65-07, Section: B, page: 3732. Adviser: Joseph Casey. Thesis (Ph.D.)--University of Windsor (Canada), 2004