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An Introduction to Multidimensional IRT

2. Why do we care about multidimensionality in measurement?. 3. Statistical Reason to Care. A fundamental assumption of unidimensional IRT models is local independence.If the latent construct being measured is actually multidimensional, this assumption may be violated.If violated, item parameter e

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An Introduction to Multidimensional IRT

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    1. 1 An Introduction to Multidimensional IRT Derek Briggs April 3, 2008 Presentation at UC Berkeley

    2. 2 Why do we care about multidimensionality in measurement?

    3. 3 Statistical Reason to Care A fundamental assumption of unidimensional IRT models is local independence. If the latent construct being measured is actually multidimensional, this assumption may be violated. If violated, item parameter estimates will be biased, and the standard errors associated with ability estimates will be too small.

    4. 4 Substantive Reason to Care It’s important to measure what you intend to measure. Test fairness—MD can cause DIF Some tests have designs that lead one to expect multidimensionality. Some tests are modeled as unidimensional, but results are reported as subscores. Multiple dimensions may be useful diagnostically.

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