A principal components analysis of the Comprehensive Test of Adaptive Behavior.

The Comprehensive Test of Adaptive Behavior (CTAB) yields indices of functioning in six categories (Self-Help Skills, Home Living Skills, Independent Living Skills, Social Skills, Sensory and Motor Skills, and Language Concepts and Academic-Skills) and a composite Total Score. A single factor, extracted through principal components analysis of standardization sample data, accounted for approximately 86% of the variance in the six category scores, portraying the CTAB as unidimensional rather than multidimensional. Therefore, rather than use of category scores, cautious interpretation of idiographic item clusters and the Total Score may be the most psychometrically sound procedure for evaluating CTAB results.