2 INVESTIGATIONS OF THE VALIDITY OF THE WISC-III

Two studies were conducted in which the validity of the WISC-III was i nvestigated. 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 eligibili ty criteria upon reevaluation with the WISC-III. Corrected correlation s between IQs were high, ranging from .80 to .87, and were comparable to figures reported in the WISC-III manual. Consistent with the WISC-I II 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 s ample of 32 students with mental retardation. The WISC-III IQs and PPV T-R scores were highly correlated, sharing between 64 to 76% of varian ce. Correlations between WISC-III IQs and scores on the WRAT-R Reading and Arithmetic subscales were moderate. Surprisingly, the WISC-III IQ s were not related to the WRAT-R Spelling scores. Implications of both studies for assessment specialists are discussed.