Two Investigations of the Validity of the WISC–III

Abstract

Two studies were conducted in which the validity of the WISC–III was investigated. In Study 1, WISC—R and WISC–III IQs were correlated for a sample of 53 students who, although originally meeting criteria for a disability category through use of the WISC—R, did not meet eligibility criteria upon reevaluation with the WISC–III. Corrected correlations between IQs were high, ranging from .80 to .87, and were comparable to figures reported in the WISC–III manual. Consistent with the WISC–III manual, WISC–III IQs were 8, 5, and 7 points lower than the WISC—R Full Scale, Verbal, and Performance IQs, respectively. In Study 2, the criterion validity of the WISC–III with the WRAT—R Reading, Spelling, and Arithmetic subscales and with the PPVT—R was investigated for a sample of 32 students with mental retardation. The WISC–III IQs and PPVT—R scores were highly correlated, sharing between 64 to 76% of variance. Correlations between WISC–III IQs and scores on the WRAT—R Reading and Arithmetic subscales were moderate. Surprisingly, the WISC–III IQs were not related to the WRAT—R Spelling scores. Implications of both studies for assessment specialists are discussed.