Purpose: Designed as a "measure of a child’s intellectual ability."
Population: Ages 6-0 to 16-11.
Scores: Verbal, Performance and their related subscale scores, and a Full Scale IQ.
Time: (50-75) minutes.
Author: David Wechsler.
Publisher: The Psychological Corporation.
Description: The WISC-III is the third generation of the Wechsler Intelligence Scale for Children. Its predecessor, the WISC-R, is the most popular and widely researched test of children’s intelligence in history.
Scoring: The WISC-III is a collection of 13 distinct subtest divided into two scales - a Verbal Scale and a Performance Scale. The six Verbal Scale tests use language-based items, whereas the seven Performance Scales use visual-motor items that are less dependent on language. Five of the subtest in each scale produce scale-specific IQS, and the 10 subtest scores produce a Full Scale IQ.
Reliability: Subtest reliabilities (expressed as internal consistencies for all but the speeded subtest of Symbol Search and Coding) are moderate to excellent (.61 to .92). The consistency of IQS and Indices is very good to excellent (.80 to .97). Subtest stability coefficients, based on 353 children subdivided into three age groups, are adequate (.56 to .89). IQ and Index stability is mostly good to excellent (.74 to .95; only one coefficient below .80). Interrater reliabilities for selected Verbal Scale subtest are excellent (all greater than .92).
Validity: The manual reports strong correlations between WISC-III metrics and comparable metrics from the WPPSI-R, WISC-R, WAIS-R, Otis-Lennon School Ability Test, and Differential Ability Scales (rs between WISC-III IQS and comparable composites range from .59 to .92). Additionally, independent studies report correlations between WISC-III IQS/Indices and comparable metrics from other batteries are well within acceptable limits. The WISC-III manual reports appropriate correlations with achievement, and studies published since test publication also report appropriate IQ-achievement correlations in children representing normal, referred, learning disabled, severely emotionally disturbed, language/speech impaired, and hearing-impaired/deaf clinical categories. The WISC-III exhibits little predictive bias when used with males, females, whites, blacks, and Hispanics.
Norms: The normative sample is large (N=2,200) and representative of 1988 U.S. Census data.
Suggested Uses: It is suggested that the WISC-III is an appropriate instrument for practitioners and clinical researchers in assessing children’s intelligence.