Estimation of premorbid intelligence from combined performance and demographic variables

Abstract

Data from the WAIS-R standardization sample was used to generate a premorbid IQ estimation formula using both demographic and current performance variables. The sample was randomly divided into two groups for development and cross-validation of the formula. Age, education, occupation, race, Vocabulary subtest raw score, and Picture Completion subtest raw score were used as predictor variables. The formulas for Verbal, Performance, and Full Scale IQ were highly significant and accurate in prediction, without the substantial restriction of range or overestimation found in other methods. Formulas for use with a lateralized population are also presented.