NAEP Scales

			Content of the Subject Area Scales Number of Items in Each Subject Area Scale Scale Composition by Item Type for New and Trend Blocks Definition of Composite Scales Ranges for the Final Subject Area Scales Correlations Among NAEP Subject Area Subscales

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 subject areas (e.g., mathematics and reading) specify multiple content-related subscales, while others (e.g., writing and all long-term trend assessment subjects) specify 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.  Since the item parameters are estimated in a different metric, the score scales must 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.

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