Comparison of the WAIS and WAIS—R: Different results for different IQ groups.

Abstract

Using a procedure that eliminated repetition of identical items, thus avoiding order effects, we administered the Wechsler Adult Intelligence Scale (WAIS) and the WAis-Revised to 108 subjects. AH correlations between the two tests were significant and similar to those reported in the WAISR manual. For the group as a whole, verbal, performance, and full scale IQ scores on the WAIS-R were significantly lower than their respective WAIS scores; however, this difference was not consistent across IQ levels. Subjects of both average and borderline intelligence had WAIS IQ scores significantly above their WAIS-R scores. For the mildly retarded subjects, the performance IQs were equal for the WAIS and WAIS-R, whereas the WAIS-R verbal and full scale IQ scores were higher than the corresponding WAIS IQ scores. However, these score differences were small (1 point) and of little practical value. The differences of moderately retarded subjects, on the other hand, were large and in the reverse direction: The WAIS-R IQ scores were significantly higher than the WAIS IQ scores. Clinical implications of these findings are discussed. When an established test is revised, evaluation of the equivalence of the two forms is necessary. Since the publication of the Wechsler Adult Intelligence Scale-Revised (WAIS-R), several comparisons of IQ scores obtained on the WAIS-R and WAIS have been published. When using subjects of average or above intelligence, the researchers generally have found lower IQ scores on the WAIS-R than on the WAIS. The exceptions to this finding are three studies, one with high-IQ subjects (Edwards & Klein, 1984) and two with mentally retarded subjects (Simon & Clopton, 1984; Spitz, 1986). The order of administration of the two forms of the Wechsler tests had an effect in some studies, but not in others. In Table 1 we provide a summary of the published literature to date on comparisons of the WAIS and the WAIS-R. Evidence that the differences between WAIS and WAIS-R scores are less at either extreme of the IQ distribution is accumulating (e.g., Mitchell, Grandy, &