General Factor Loadings and Specific Effects of the Differential Ability Scales, Second Edition Composites.

The purpose of this study was to investigate the g loadings and specific effects of the core and diagnostic composite scores from the Differential Abilities Scales, Second Edition (DAS-II; Elliott, 2007a). Scores from a subset of the DAS-II standardization sample for ages 3:6 to 17:11 were submitted to principal factor analysis. Four composites, Nonverbal Reasoning Ability, Verbal Ability, Spatial Ability, and Working Memory, appear to be primarily measures of the general factor across most age levels. In contrast, Processing Speed appears to primarily be a measure of a specific ability or specific abilities across age levels. A secondary analysis revealed that averaging subtest g loadings produced downwardly biased values for composites, that the Spearman (1927) formula for determining the g loading of a composite produced upwardly biased values, and that averaging subtest specific effects produced upwardly biased values for composites. [ABSTRACT FROM AUTHOR]