Date of Award

1995

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Psychology

Abstract

This study investigated the criterion-related validity of the Test of Cognitive Skills (TCS) as an estimate of cognitive ability for students with learning disabilities. Research indicates that knowledge of scores from group ability tests significantly influences teachers' instruction and treatment of students. In contrast, school psychologists rarely consider group administered test scores and must devote substantial time to administering and interpreting individual intelligence measures. The present study compared the TCS to the Wechsler Intelligence Scale for Children - Revised (WISC-R) for students with learning disabilities in order to contribute to the valid use of the TCS by both teachers and school psychologists. More specifically, the study examined the validity of using the TCS (a) to screen for students with learning disabilities, and (b) as a substitute for the WISC-R as an estimate of cognitive ability for students with learning disabilities. Subjects were 118 elementary and middle school students enrolled in learning disability services in a midwestern county school system. Results of t-tests indicated that the TCS Cognitive Skills Index (CSI) significantly underestimated the cognitive abilities operationally defined by the WISC-R. Pearson correlations revealed significant positive relationships between the CSI and each of the WISC-R IQs and factor scores. The standard error in estimating the WISC-R Full Scale IQ (FSIQ) from the CSI was 8.19 standard score points; thus, a confidence range of approximately 33 points was required to estimate the FSIQ from the CSI at a 95% probability of accuracy. Post-hoc analyses revealed that subjects tended to score lower on the CSI as FSIQ-CSI differences increased. Further, subjects with weaknesses in reading skills obtained significantly lower CSIs than subjects with average reading skills. The FSIQs of these two groups were not significantly different. Moreover, subjects with weaknesses in attention/concentration skills obtained significantly lower CSIs than subjects with average attention/concentration skills. However, as measured by the WISC-R Verbal Comprehension factor, the cognitive abilities of these two groups were not significantly different. Based on the results of this study, the TCS CSI cannot be recommended as an estimate of cognitive ability as operationally defined by the WISC-R for students with learning disabilities. Further, using the CSI in screening students for learning disabilities is contraindicated since the CSI is likely to screen out students with learning disabilities. Additional research is required to examine the validity of the CSI as an estimate of cognitive ability for both specialEducation and regularEducation.

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