Confirmatory factor analysis of the Wechsler Memory Scale-Revised standardization sample.

A maximum likelihood confirmatory factor analysis was preformed by applying LISREL to the variance-covariance matrix obtained from standardization of the Wechsler Memory Scale-Revised (WMS-R) (N = 316). Analyses were designed to determine which of seven hypothesized factor solutions could best explain memory function as measured by the WMS-R. Competing latent variable models were identified in previous exploratory and confirmatory factor analytic studies. The measurement error matrix was set to remove method variance shared by the immediate and delayed trials of the same subtest. Hypothesized factors were fixed and allowed to correlate. Results indicated that a three-factor model, including Attention/Concentration, Immediate and Delayed Memory, explained 91% of the score variance and produced a significantly better fit than the Attention/Concentration--General Memory or Attention Concentration--Visual/Verbal Memory solutions. Findings support previous work suggesting that the WMS-R measures separate memory functions, and that the verbal/nonverbal Index distinction may not be a viable one.