The properties of equally and differentially weighted WAIS-III factor scores

Two methods of differential weighting including reliable component analysis (RCA) were compared with equal weighting in calculating factor scores for the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III; D. Wechsler, 1997). Differentially weighted scores were highly replicable across samples. Equal weighting provided scores that were most reliable followed by RCA weighting. Equally weighted scores were highly intercorrelated, whereas differentially weighed scores were uncorrelated. Equally weighted scores were more confounded with g than differentially weighted scores. RCA score differences were substantially more reliable than those of equal weighting. The 2 most reliable, orthogonal components that can be formed from the WAIS-III subtests are measures of Gf and Gc, not verbal and performance IQs, but the 4-factor model resembled that suggested in the WAIS-III manual. The use of RCA to define the factor scores results in scores with several attractive properties.