The stability of WISC -III scores: For whom are triennial re -evaluations necessary?

Linda C Cassidy, University of Rhode Island


This study investigated the long-term stability of Verbal, Performance and Full Scale IQ scores for a sample of exceptional children evaluated with the Wechsler Intelligence Scale for Children-Third Edition (WISC-III) as part of the mandated three-year re-evaluation process. Archival data were collected from the special education files of 592 children who were administered the WISC-III on two separate occasions between September, 1992 and June, 1996 from twenty-seven school districts in a small New England State. Several variables (special education classification, Full Scale IQ score at initial administration, age of participant at initial administration, as well as the ethnicity and gender of the participants) were examined to detect which variables, if any, would influence the stability of test scores over the three-year interval. Three statistical analyses for measuring stability (correlational method, test of mean difference and test of intra-individual variability) were conducted. Results indicated that for this sample of children in special education, examined as a group, Verbal IQ, Performance IQ and Full Scale IQ scores remain stable over time. However, certain populations demonstrated significant instability in scores over the three-year interval. Results suggested that children classified as mentally retarded or behavior disordered fluctuate significantly in their performance on the WISC-III over a three-year interval. Similarly, children who receive an initial Full Scale IQ score above 109 demonstrate significant instability in scores between administrations. Therefore, for these populations, three-year re-evaluations appear necessary. However, routine administrations of the WISC-III for all children involved in special education is of questionable value. Further research must be done to confirm the findings of this study in order to assist policy makers in distinguishing which children would benefit from a three-year re-administration of the WISC-III and for which children such information would yield no further information. ^

Subject Area

Education, Tests and Measurements|Education, Special|Psychology, Psychometrics|Psychology, Cognitive

Recommended Citation

Linda C Cassidy, "The stability of WISC -III scores: For whom are triennial re -evaluations necessary?" (1997). Dissertations and Master's Theses (Campus Access). Paper AAI9805230.