Two indices of subtest scatter on Wechsler's Intelligence Scales: estimated vs. empirical values.

Previous research on the scaled-score range and the number of deviant subtest scores on the WISC-R and the WPPSI has produced surprising results: Normal children exhibited much more scatter than most clinicians probably realized. Yet, in principle, these results were predictable from a knowledge of the statistical properties of scaled scores. Procedures for evaluating the abnormality of the two indices of scatter are presented and their accuracy checked against the actual distributions of the indices for the two standardization samples. The findings suggest that the procedures are sufficiently accurate for most clinical applications, which supports their use when the actual distributions of the indices are unknown.