A confirmatory factor analysis of the WAIS-III in a clinical sample with crossvalidation in the standardization sample.

A maximum likelihood confirmatory factor analysis of the Wechsler Adult Intelligence Scale-III (WAIS-III) was performed by applying LISREL 8 to a clinical sample (n=328). Analyses were designed to determine which of the nine hypothesized oblique factor solutions could best explain intelligence as measured by the WAIS-III in the general clinical sample. Competing latent variable models were identified in previous studies and a priori model modifications were made to test derivations of the nine base models. Results in the clinical sample were crossvalidated by testing all models in the normative sample used in the standardization of the scale. Findings in both the clinical and standardization samples supported a six-factor model including Semantic Memory, Verbal Reasoning, Constructional Praxis, Visual Reasoning, Working Memory, and Processing Speed factors. Our analysis differed from that presented in the WAIS-III manual as we tested more complex models of intelligence in addition to the ones evaluated by the test publishers. As a result, a six-factor model that corresponded to an expanded version of a model based on Horn's Gf-Gc theory was empirically supported as having the best fit to the data. More complex derivations of this model failed to achieve sufficient goodness of fit.