Saturday, December 11, 2010

Dissertation Dish: WISC-IV and WJ III relationship in clinical referral population

The relationship between the Wechsler Intelligence Scale for Children-Fourth Edition and the Woodcock-Johnson III Tests of Cognitive Abilities in a clinically referred pediatric population by Shaw, Lindsay Anne, Ph.D., Nova Southeastern University, 2010 , 157 pages; AAT 3427690


This research involves an investigation of the construct validity of the Wechsler Intelligence Scale for Children- Fourth Edition (WISC-IV) when compared to the Woodcock-Johnson III Tests of Cognitive Abilities (WJ III COG) to provide evidence for the utility of using the WISC-IV in assessing cognitive abilities according to the Cattell-Horn-Carroll (CHC) theory. The study was conducted using archival data consisting of 92 children and adolescents between the ages of 6 years and 16 years, 11 months referred for a comprehensive neuropsychological evaluation at a university-affiliated assessment center. Data for all participants were collected following administration of a battery of measures as part of a neuropsychological evaluation, with tests administered in no particular order. The mean age of children was 9.82 years ( SD = 2.81) with a mean grade level of 3.95 ( SD = 2.63). Ten hypotheses were investigated specifically to examine the comparability of the general intellectual functioning scores for each battery among a sample of children with neuropsychiatric disorders, as well as to examine the convergent and discriminate validity of the WISC-IV index scores. The first hypothesis utilized a paired samples t-test and found that the WISC-IV Full Scale IQ score was significantly below that of the WJ III COG General Intellectual Ability-Extended score. For the remaining hypotheses, Pearson product-moment correlations revealed large correlations between the WISC-IV and WJ III COG convergent constructs of general intellectual functioning, comprehension-knowledge, fluid reasoning, working memory, and processing speed. For correlations between divergent constructs, the WISC-IV Verbal Comprehension Index and the WJ III COG Visual-Spatial Thinking ( Gv ) factor demonstrated a large correlation. Both the WISC-IV Processing Speed Index and Working Memory Index correlated moderately with the WJ III COG Gv factor, while the WISC-IV Perceptual Reasoning Index correlated moderately with the WJ III COG Auditory Processing factor. Fisher's r to Z transformation was used to assess for significant differences between the observed correlations and stipulated values determined. Results indicated that correlations between the global IQ, fluid reasoning, and short-term memory composite scores of the two measures were significantly greater than that found for the WISC-III and WJ III COG, while the relationship between the verbal ability and processing speed composite scores were consistent with past findings. Correlations between divergent constructs revealed a reliable pattern of significantly greater relationships than was found for research concerning the WISC-III and WJ III COG. Primarily, results of this study provided evidence that the substantive changes made to the WISC-IV have improved the ability to interpret the Full Scale IQ score as a measure of general intelligence similar to that obtained by the WJ III COG. However, the global IQ scores between the two measures cannot be assumed to be equivalent among children with neuropsychiatric disorders. Results also suggested that the WISC-IV appears to provide improved measurement of the CHC broad abilities of fluid reasoning ( Gf ) and short-term memory ( Gsm ). Correlations between divergent constructs provided evidence for relationships between cognitive abilities suggested to be significantly related to academic achievement. This study concluded that research findings for the WISC-III cannot be applied conclusively to the WISC-IV and that the substantive changes made to the WISC-IV have improved the ability to interpret the battery under the CHC framework. However, findings underscore the importance of examining performance across second-order factors that may contribute to differences in general intelligence, as well as remaining aware of differences in narrow ability constructs measured, task demands, or shared variance between subtests when making interpretations of test performance.

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