Estimation of WAIS-III intelligence from combined performance and demographic variables: development of the OPIE-3

Data from the WAIS-III standardization sample (The Psychological Corporation, 1997) was used to generate several FSIQ estimation formulas that used demographic variables and current WAIS-III subtest performance. The standardization sample (N=2,450) was randomly divided into two groups, the first was used to develop the formulas and the second group was used to validate the prediction equations. Age, education, ethnicity, gender, region of the country as well as Vocabulary, Information, Matrix Reasoning, and Picture Completion subtests raw scores were used as predictor variables. Regression formulas were generated using four subtest, two subtest, single verbal, two performance subtest, and single performance algorithms. The four-subtest model combined Information, Vocabulary, Matrix Reasoning, and Picture Completion raw scores with demographic variables. The two-subtest algorithm used Vocabulary and Matrix Reasoning raw scores with demographic variables. Formulas to estimate FSIQ using only verbal or performance subtests were developed for use with lateralized populations. The formulas for estimating premorbid FSIQ were highly significant and accurate in predicting FSIQ scores of participants in the WAIS-III normative sample.