Estimation of General Intelligence in Neurological Settings by a Short Form of the WAIS-IV

Objective: Standardization and psychometric evaluation of a short-form index (derived from subtests vocabulary and matrix reasoning) for the German language WAIS-IV, with discussion of implications for clinical practice. Method: Analyses are based on the standardization sample of the German edition of the WAIS-IV (N = 1 425), with all norming procedures identical with the original scales. Confidence limits rely on the standard error of the estimate to achieve a correction for regression towards the mean. Test criteria with a practical relevance are presented (critical differences along with base rates, reliabilities). Results: Battery reliability of the composite index (short form) amounts to r = 0.94), its correlation with the full-scale WAIS-IV IQ is given by r = 0.86. Differences between short-form composite index and full-scale WAIS-IV IQ fall below the critical difference in 71 % of the sample. Full-scale IQ may be gauged from the short-form index by IQ approximate to 14.254 + 0.857* KF-IQ (variance explained by regression: 73 %, RSME = 7.77; cross-validated by oversampled fraction of the norming sample: N = 202, WAIS-IQ = 101.0; 15.07). Conclusion: A WAIS-IV short form may be a viable method of assessment in specific clinical settings. This notwithstanding, reliable diagnoses should rely on application of the complete set of subtests.