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Testing the Local Independence Assumption in Item Response Theory IRT

Rosenbaum, Paul R.
Publication Year:
Report Number:
ETS Research Report
Document Type:
Page Count:
Subject/Key Words:
Advanced Placement Examinations, Biology Tests, Item Analysis, Item Response Theory (IRT), Statistical Analysis


Local independence and monotone increasing item characteristic curves imply nonnegative conditional covariances between all monotone increasing functions of a set of item responses given any function of the remaining item responses. This general result provides a basis for testing the local independence assumption without first specifying a parametric form for the item characteristic curve. The proposed tests are simple, have known asymptotic null distributions, and posses certain optimal properties. In an example, the local independence hypothesis is rejected for all possible forms of the monotone item characteristic curves. (30pp.)

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