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Differential Ability Scales (DAS)


FACTOR ANALYSIS OF THE DAS

Factor Analysis reported in the DAS Introductory and Technical Handbook reports a series of both confirmatory and exploratory factor analyses of the standardization sample. The results indicated that, for the most part, the structure of abilities assessed by the DAS becomes more distinct as the child’s age increases. One factor provided the best fit for the core subtests for the youngest children, two factors emerges as the child’s cognitive abilities increase, and a final, three-factor model is the best fit for the abilities of the school-age child. In addition to the factors created from the robust g-saturated subtests, the lower g-loaded diagnostic subtests provide additional information about a child’s ability, independent of the core subtests.

Further support for the factors of the DAS was provided by both independent analysis of the DAS standardization sample (Keith 1990; Stone, 1992) and analysis of a separate, smaller sample of children (Byrd & Buckhalt, 1991). Keith (1990) found that there was strong support for concluding that the constructs measured by the DAS are "remarkably consistent across the overlapping age levels of the test" (p. 403). Although he chose to label the DAS Spatial factor "Nonverbal Reasoning" and the Nonverbal Reasoning factor "Gf," Keith accepts that the DAS Verbal, Nonverbal Reasoning, and Spatial factors are good measures of Gc, Gf, and Gv respectively. Stone (1992) found support for the three-factor structure of the core subtests for school-age children: Verbal, Nonverbal Reasoning, and Spatial Abilities.

Using a multitrait-multimethod analysis of construct validity, Byrd and Buckhalt found support for the overall general conceptual ability (GCA) and the specificity of selected subtests for profile analysis. Although several researchers have questioned how well the names of the DAS clusters describe the constructs they measure, it is generally assumed that the DAS Nonverbal Reasoning may be considered a strong measure of Fluid intelligence (Gf) (Keith, 1990, Elliott, 1990). This assumption has both empirical (Keith 1990, 1997; McGhee, 1993) and theoretical (McGrew, 1997; McGrew & Flanagan, 1998) support. Using the The McGrew, Flanagan, and Ortiz Integrated Carroll/Cattell-Horn model of abilities, the DAS Verbal cluster most likely represents Crystallized Intelligence (Gc) while the Spatial Cluster reflects primarily Visual Processing (Gv) (McGrew & Flanagan, 1998, ch. 4, Appendix A).

 

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Measures of g