Analysis of the WAIS-III Index score scatter using the significant deviation from the mean of the four Index scores

Despite their validity and their potential clinical interest, the WAIS-III Index scores seem less used by clinicians than the traditional IQs. One of reason of this lack of interest in the Indices is the relative complexity of their interpretation. We advocate the use of the average index score as a baseline to analyze the Index score variability and to identify strengths and weaknesses in the profile of the Index scores. Davis's formula provides reference values to be used to highlight the Index scores significantly moving away from the baseline. The usefulness of this method is illustrated with the analysis the Index score scatter in the standardization sample of the French adaptation of the WAIS-III. A rather important dispersion of the Index scores around the average index score was observed, a large percentage of standardization sample showing one or two Index scores significantly different from the baseline.