The long-term stability of WISC-R scores in mildly retarded and learning-disabled children

Abstract

This study addresses the need for systematic longitudinal research documenting the stability of WISC-R scores in special education populations. WISC-R scores of 100 learning-disabled and 60 mildly retarded children retested on three separate occasions at three-year intervals were examined. The stability of WISC-R scores was evaluated according to three different criteria: (a) the consistency of group means over time, (b) the frequency of significant changes in individual scores, and (c) correlations between administrations as an index of stability of subjects' relative positions in the group. Different results were obtained depending on the criterion considered. Examination of group means and correlation coefficients indicated that Full Scale IQ was fairly stable over a period of six years for both learning-disabled and mildly retarded samples. However, greater variability was noted when examining the frequency of changes in individual subject's scores. Verbal IQ and Performance IQ demonstrated somewhat more variability by all criteria examined. The implications of these results with regard to the importance assigned to IQ in special education classification decisions, the usefulness of retesting IQ in three-year reevaluations, and the efficacy of special education are discussed.