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The WAIS was administered twice to 204 institutionalized adult retardates, with a mean retest interval of 32 mo. Full Scale IQs on retest were within 8 points of initial Full Scale IQs for over 90% of the retardates and a test-retest reliability coefficient of .90 was obtained. These results demonstrate the high reliability and stability of WAIS Full Scale IQs for adult retardates.
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Dinning et al. (1977) studied this question.
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