Subtest scatter as an indicator of the inaccuracy of short-from estimates of IQ.

Short-forms of Wechsler intelligence tests have abounded in the literature and have been recommended for use as screening instruments in clinical and research settings. Clinicians who administer short-forms as screening devices are concerned with the accuracy of the resulting IQ estimate. LoBello recently recommended that subtest scatter might serve as an indicator that the resulting short-form IQ does not accurately estimate the IQ based on the entire scale. In this study, the data from 69 children who had taken the WPPSI-R were used to estimate the correlation for the differences between Full Scale WPPSI-R IQs on the complete test and on the short-form (four subtests) and the differences between the subtests with the highest and lowest scaled scores. The Pearson r of .02 indicates that subtest scatter is not related to the accuracy of the short-form IQ and will not reliably alert clinicians to the need to administer the entire battery.