NAEP Scales
NAEP scales are determined a priori by grouping items into content domains for which overall performance is deemed to be of interest. The content domains are defined by the frameworks, which have been the responsibility of the National Assessment Governing Board since 1998. Frameworks for some subjects specify content-related subscales, while others specify only a single scale. When subscales are specified, a composite scale is created from the subscales. The frameworks specify the weights assigned to each of the subscales when a composite scale is created. There is a linear indeterminacy in Item Response Theory (IRT) scales. In other words, if the item parameters are estimated in a different metric, the score scales could be transformed to make the equations describing the models true. Final results for each subject area are linearly transformed from the original scale to a 0–500 or a 0–300 scale. Last updated 14 July 2008 (DB) |
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