Measurement invariance of core cognitive abilities in heterogeneous neurological and community samples

Confirmatory factor analysis of Australian adaptations of combined Wechsler Adult Intelligence Scale-Revised (WAIS-R) and Wechsler Memory Scale-Revised (WMS-R) scores was conducted in a sample of 277 participants undergoing investigation for neurological disorders. The best-fitting model was a six-factor model representing the latent abilities of Verbal Comprehension, Perceptual Organization, Working Memory, Verbal Memory, Visual Memory, and Processing Speed. Invariance of the measurement model was then examined in the mean and covariance structure with data from a recent Australian normative study of the WAIS-R and WMS-R. [Carstairs J.R. & Shores E.A. Aust Psychol 35 (2000) 36-40]. Results suggest that the measurement model underlying test scores displayed “strong” metric invariance [Widaman, K. F., & Reise, S. P. (1997). Exploring the measurement invariance of psychological instruments: Applications in the substance abuse domain. In K. J. Bryant & M. Windle (Eds.), The science of prevention: Methodological advance from alcohol and substance abuse research (pp. 281–324). Washington, DC: American Psychological Association] across clinical and community samples. These findings satisfy assumptions necessary for uncomplicated interpretation of validity correlations and differences in test scores across groups.