Jb. Hale et al., WISC-III predictors of academic achievement for children with learning disabilities: Are global and factor scores comparable?, SCH PSYCH Q, 16(1), 2001, pp. 31-55
The Wechsler Intelligence Scale for Children-Third Edition (WISC-III) provi
des a Full Scale Intelligence Quotient (FSIQ), four factor standard scores,
and subtest scale scores. Although the incremental validity of the WISC-II
I factor scores over FSIQ in predicting academic achievement has been quest
ioned, this finding was based on the assumption that FSIQ should be entered
first into the regression equation and failed to examine the shared varian
ce among predictors. In contrast with previous findings, this study of 174
children meeting criteria for learning disabilities revealed that the WISC-
III factors accounted for a large portion of achievement variance during hi
erarchical regression analyses, yet FSIQ added little predictive power. A c
ommonality analysis of FSIQ indicated that it is largely comprised of uniqu
e, not shared, factor variance. Analyzing the WISC-III subtests from a Gf-G
c theoretical framework, academic achievement commonality analyses revealed
complex relationships among the predictors, with crystallized, quantitativ
e, and short-term memory factors accounting for the most achievement varian
ce, regardless of academic domain. Results suggest that simple rejection of
factor or subtest scores based on hierarchical regression techniques is un
warranted and that systematic exploration of nomothetic and idiographic pat
terns of performance is recommended for practitioners.