Base rate data for the WAIS-R: test-retest stability and VIQ-PIQ differences.

The data analyzed were the 14 WAIS-R scores from each of the individuals who comprised the WAIS-R standardization sample. Examined was the individual VIQ-PIQ difference from only the initial examination of each of the 1880 subjects, as well as the test-retest change in each of the 14 WAIS-R scores for each of the 119 subjects who were retested. The results revealed that, although the WAIS-R has excellent psychometric reliability as reflected in its standard error of measurement of a VIQ-PIQ difference and its impressively high test-retest Pearson r values, the actual magnitudes of the differences between the VIQ and PIQ assessed in a single examination, or the magnitudes of gain or loss in the 14 scores on retest, for some of these normal individuals were sufficiently high that such base-rate data should be routinely considered by clinical neuropsychologists and other practitioners.