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Differential Ability Scales (DAS)


STANDARDIZATION OF THE DAS

The DAS was standardized on 3,475 children selected to be representative of non-institutionalized, English-proficient children aged 2 years 6 months through 17 years 11 months living in the United States during the period of data collection (spring 1987 through spring 1989). Although the DAS standardization excluded those children with severe disabilities (since for these children the DAS would be inappropriate), it did include children with mild perceptual, speech, and motor impairments, if the examiner judged that the impairments did not prevent the valid administration of the test. The demographic characteristics used to obtain a stratified sample were age, sex, race/ethnicity, parental educational level, educational preschool enrollment, and geographic region. An additional 600 Black and Hispanic children were tested during standardization to enable accurate analysis of item bias, as well as to help ensure that item-scoring rules would be sensitive to minority children’s responses. These additional children were not included in the norms calculation.

For race/ethnicity membership, individuals were classified as White (N = 2443), African American (N = 525), Hispanic (N = 382), and Other (N = 125). The four parental education categories ranged from less than 12 years of education to at least 16 years of education. The four geographic regions sampled were Northeast, North Central, South, and West. Parents in the White and Other classifications had the most education—50.8% of the White group and 56.9% of the Other group had some college education, while 29.2% of the African American group and 19.1% of the Hispanic group had some college education. The majority of the White and African American children came from the North Central and South regions, while the majority of the Hispanic and Other children came from the South and West. The race/ethnic proportions in the sample were 70.3% White, 15.2% African American, 11.0% Hispanic, and 3.5% Other. Demographic characteristics were compared to the March 1988 Current Population Survey of the U.S. Bureau of the Census and were matched across as well as within categories (i.e., age x sex x race, age x sex x parent education, age x sex x region, race x region, and age x race x parent education). Total sample percentages of these categories and subcategories were very close to the Bureau of the Census data and never different by more than 0.6 percentage points. There were variations among the 18 age groups.

In the standardization sample, there were 18 age groups: 2:6-2:11, 3:0-3:5, 3:6-3:11, 4:0-4:5, 4:6-4:11, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 and 17 years. In each six-month age group between 2years 6 months and 4 years 11months, there was a total of 175 children, while from ages 5 through 17 there were 200 children in each one-year age group. In each six-month age group between 2 years 6 months and 4 years 11months, there were approximately equal numbers of males and females, while for all remaining age groups there were 100 males and 100 females per group. This sampling methodology was excellent. Small (under 100,000) and large (over 1,000,000) communities were slightly underrepresented.

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Reliabilities