Inverse relationship between the WISC-R/WAIS-R score disparity and IQ level in the lower range of intelligence

The WISC-R and WAIS-R Full Scale IQs of nine groups of subjects (two from the present study and seven from previously published studies) that had mean WISC-R IQs ranging from 45 to 81 were compared. The WAIS-R produced higher IQs than did the WISC-R, and this disparity increased as WISC-R IQ decreased. A regression equation for this function was given. The progressive disparity was due in large part to differences in raw score to scaled score conversions compounded by differences in tabled values for converting scaled scores to IQs.