College of Psychology: Faculty Proceedings, Presentations, Speeches and Lectures


Rates of Apparently Abnormal WAIS-4 Patterns in the Normal Population


C. Carroll

Event Location / Date(s)

Marco Island, FL / November 16-19, 2011

Document Type

Conference Proceeding

Presentation Date


Conference Name / Publication Title

31st Annual Meeting of the National Academy of Neuropsychology



Objective: Interpretation of the WAIS-4 involves examination of patterns of index and subtest scores. Base rate data from the standardization sample suggest that 15-point differences between index scores or 3-point differences between a subtest and the subtest mean are uncommon in normal individuals, but these data refer to a single index or subtest comparison rather than multiple comparisons among indexes or subtests.

Method: The normal incidence of index and subtest score differences was calculated using Monte Carlo simulations. Correlations among scales from the standardization sample were used to recreate the distributions of expected scores using the scale variance and covariance information contained in the correlation matrix. The frequency of observed index or subtest discrepancies was then determined. Results: One or more 15-point index score difference occurred in 49% of normal individuals. Differences in 20 points between any two indexes occurred in 35% of the normative sample, and at least one 25-point index difference was present in 16% of the normal population. Seventy-eight percent had at least one subtest score and 47% had two or more subtests that were three points below their subtest mean. Sixty-one percent had one or more subtests that were four points lower, and 25% had one or more subtests five points lower than their subtest mean.

Conclusions: WAIS-4 index or subtest score discrepancies are normally common when all possible such comparisons are made, and this reduces their clinical significance. Specific prior interpretive hypotheses are necessary to reduce the number of Index or subtest comparisons and associated false-positive conclusions.

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