Predicting WAIS-R IQ premorbid ability: combining subtest performance and demographic variable predictors.

The WAIS-R standardization sample was used to develop regression formulas designed to predict WAIS-R IQ scores. In contrast to previous approaches that focused on either "hold" measures or demographic variables as predictors of premorbid functioning, these two domains were used conjointly in the present study. WAIS-R subtests served as measures of present ability, whereas age, race, sex, education, and occupation served as the demographic predictors. Because any WAIS-R subtest may be impaired following brain injury, no subtest(s) were determined a priori to be "hold" measure(s). Instead, 33 regression formulas were developed each combining 1 of the 11 WAIS-R subtests with demographic variables, to predict IQ scores. The current equations generally doubled the amount of variance accounted for by demographic variables alone and accounted for more variance in WAIS-R IQs than any other currently available method of predicting premorbid cognitive functioning. Regression to the mean was not a significant problem. The regression equations are reported to aid in the estimation of premorbid WAIS-R IQ. Tables of predictive accuracy are also presented.