Ipsative comparisons of WISC-IV index scores.

The Wechsler Intelligence Scale for Children-4th Edition (Wechsler, 2003a) yields standard scores for four indexes that can be compared when practitioners examine within-child variability. The test manual provides pairwise comparison tables that clinicians can use to examine the scale variability, but it does not adequately caution them about the statistical pitfalls of multiple pairwise comparisons (e.g.