DIFFERENCES BETWEEN WISC-III AND WISC-R IQS - A PRELIMINARY INVESTIGATION

Differences between WISC-III and WISC-R IQs of 257 children (118 with Specific Learning Disability, 79 with Mental Retardation, and 60 who w ere not classified as disabled) were examined. As anticipated, the WIS C-III and WISC-R IQs were highly correlated, ranging from .84 for the Full Scale IQs to .80 for the Performance IQs. The WISC-III Full Scale , Verbal, and Performance IQs were 7.2, 5.8, and 7.5 points lower than corresponding WISC-R values. The size of the difference between WISC- III and WISC-R IQs was correlated significantly with WISC-R (r = .34) and WISC-III (r = -.23) IQs. Differences in the size of the ra drop we re in part a function of disability group membership: Students with le arning disabilities differed in the likelihood of increases and decrea ses in IQs in comparison to students with mental retardation. Sex was unrelated to the size of the IQ drop. Amount and direction of change w ere predicted by subtest scores. Importantly, high Object Assembly and Coding scores were primary factors in predicting increases in IQ, and higher Vocabulary scores predicted decreases in IQ.