Differential Ability Scales

Purpose: Designed to assess the cognitive ability and achievement of children.

Population: Children, aged 2 years 6 months through 17 years 11 months.

Scores: General Conceptual Ability, cluster scores and core subtest scores.

Time: (25-65) minutes for Preschool level, (40 –65) minutes for School-Age Level on the Cognitive Battery,  (15-25) minutes for the School Achievement tests.

Author: Colin D. Elliott

Publisher: The Psychological Corporation

Description: The Differential Ability Scales is an individually administered test battery intending to measure cognitive and achievement levels for children for classification and diagnostic purposes.  Its diverse nature makes it possible to profile a child’s strengths and weaknesses. This instrument intends to provide a wider range of measurement possibilities than found in other similar batteries. The tasks and scores of the DAS are said to reflect a wide range of theories to accommodate a variety of theoretical views. It consists of 20 subtests, 17 cognitive and 3 achievement subtests yielding an overall cognitive ability score and achievement scores.  Differences between cognitive abilities and between cognitive ability and achievement can be explored.  Harder or easier sets of items can be administered if high or low ability is expected in out-of-level testing.

Scoring: Scores are obtained on three levels, the General Conceptual Ability (GCA) made up the cluster scores, with a foundation provided by the individual subtests.  The GCA score is based on a definition of psychometric g as the general ability of an individual to perform complex mental processing that involves conceptualization and the transformation of information (conceptual and reasoning ability), the cluster scores represent verbal, spatial, and nonverbal reasoning abilities, and the subtest represent specific ability or processes.  Special ability scores for Verbal Ability, Nonverbal Reasoning Ability, and Spatial Ability are reported as percentiles and standard scores.  Such measures as perceptual and memory skills on the diagnostic subtest are reported by age as both percentile and T scores.

Reliability: The reliability coefficient (IRT in most cases,) was high for The GCA in all ages, with an average of .90 at the lowest preschool lever, and .94 for the upper pre school level.  And .95 for the School Age level.  Test-retest reliability scores were very stable for the GCA and cluster scores. Ranging from .79 to .94.   Tests with high internal reliability were also found to have high test-retest reliability.

Validity:  Inter-correlation of subtests and composites by age ranges were 100.3 and 99.7 for GCA, and SNV for ages 2:6 –3:5, 99.6 and 99.8 for ages 3:6-5:11. There were high correlations between the DAS and the WPPSI-R on the composite scores for 4 and 5 year olds.  The correlations between the verbal composites of the and the DAS  and the SB-IV composites were reasonably high, at .74 to .77 for 4 and 5 year olds. Correlations with the McCarthy Scales of Children’s Ability (MSCA) showed highest correlations with the Verbal, Perceptual-Performance, or Qualitative scales.  For school age level all of the DAS composites correlated highly with the WISC-R Full Scale IQ, and the DAS Verbal ability cluster correlated very highly with the WISC-R Verbal IQ for 8 to 10 year olds and for 14 to 15 year olds.  The verbal composites of the DAS and the SB-IV for 9 to 10 year olds also correlated very highly.

Norms: The normative sample included 3,475 children and adolescents representative of the US population census for race/ethnicity, gender, community size, and parent education.

Suggested use:  According to the author, the GCA of the DAS is an excellent predictor of academic achievement.  This instrument is able to address a wide variety of referral questions for a broad age range of children in school and clinical settings, as well as in research.