Differential Ability Scales
The DAS has excellent reliability. Average internal consistency reliability
coefficients for the GCA, based on the 13 whole-year age groups, are .90, .94,
and .95 (Lower Preschool, Upper Preschool, and School-Age respectively), .88 for
the Verbal Scales (Upper Preschool and School-Age), .89 and .90 for Preschool
Nonverbal ability and School-Age Nonverbal Reasoning ability, and .92 for the
Spatial ability scores.