Base rates of WAIS-R subtest scatter as a guide for clinical and neuropsychological assessment.

Data from the WAIS-R standardization sample (N = 1880, ages 16-74) were analyzed to determine normal base rates of subtest scatter and to discover whether the amount of scatter is related significantly to various stratification variables. Two indices of scatter were computed for the Verbal, Performance, and Full Scales: range (highest minus lowest scaled score) and number of subtests that deviated significantly from a person's own mean. ANOVAs conducted with the range statistic showed that scatter on all three WAIS-R IQ scales was related significantly to education level; that Blacks had less scatter than Whites on the Verbal and Full Scale; and that females had less scatter than males on the Verbal scale. Base rate normative tables of subtest scatter were presented for five different levels of Full Scale IQ. Implications of these tables for clinical and neuropsychological assessment were discussed.