Accuracy of estimates of premorbid intelligence based on demographic variables

Regression equations have been presented for estimating premorbid IQs on Wechsler's intelligence scales, using the demographic variables employed to stratify the various standardization samples as predictors. The accuracy of the resulting estimates for classifying patients into Wechsler's seven IQ categories (from very superior to mentally retarded) was evaluated, and it was found that even the best estimates can be expected to misclassify more than half of all patients. Such estimates still can contribute to valid inferences about a patient's premorbid intelligence, but only when they are used in conjunction with information from other sources.