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., inflated error rate). An alternative to the pairwise comparison approach called an ipsative method can be used to compare the 4 WISC-IV standard scores to an individual child's mean of the 4 index scores with more control over the error rate. These values were computed at the .05 and .01 levels following the method used by Naglieri (1993) for the Wechsler Intelligence Scale for Children-3rd Edition (WISC-III; Wechsler, 1991) as originally suggested by Davis (1959) and modified by Silverstein (1982) for previous versions of Wechsler's scales and other multiscore intelligence tests. An example of the use of the technique is provided, as are interpretive cautions.