Intratest and Intertest Reliability and Stability of the Wisc, Wisc-R, and Wais Full Scale Iqs in a Mentally Retarded Population

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Abstract
The reliability and stability of the Full Scale IQ scores of retarded adolescents and young adults on 3 Wechsler Scales were measured. For mean retest intervals ranging from about 1.75 to 3.5 years, intratest reliability and constancy were reasonably good, although a significant rise in mean IQ was found for the WISC-R retest. Intertest reliability was also inadequate, but intertest constancy was not. The mean WISC-R IQ was significantly lower than the mean WISC IQ, and both were dramatically lower than the mean WAIS IQ. Comparisons are made with previous findings and implications of these results are discussed.