Parsimonious prediction of Wechsler Memory Scale, Fourth Edition scores: immediate and delayed memory indexes

Research on previous versions of the Wechsler Memory Scale (WMS) found that index scores could be predicted using a parsimonious selection of subtests (e.g., Axelrod & Woodard, 2000). The release of the Fourth Edition (WMS-IV) requires a reassessment of these predictive formulas as well as the use of indices from the California Verbal Learning Test-II (CVLT-II). Complete WMS-IV and CVLT-II data were obtained from 295 individuals. Six regression models were fit using WMS-IV subtest scaled scores-Logical Memory (LM), Visual Reproduction (VR), and Verbal Paired Associates (VPA)-and CVLT-II substituted scores to predict Immediate Memory Index (IMI) and Delayed Memory Index (DMI) scores. All three predictions of IMI significantly correlated with the complete IMI (r = .92 to .97). Likewise, predicted DMI scores significantly correlated with complete DMI (r = .92 to .97). Statistical preference was indicated for the models using LM, VR, and VPA, in which 97% and 96% of the cases fell within two standard errors of measurement (SEMs) of full index scores, respectively. The present findings demonstrate that the IMI and DMI can be reliably estimated using two or three subtests from the WMS-IV, with preference for using three. In addition, evidence suggests little to no improvement in predictive accuracy with the inclusion of CVLT-II indices.