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Graphical IRT-Based DIF Analyses DIF IRT

Pashley, Peter J.
Publication Year:
Report Number:
ETS Research Report
Document Type:
Page Count:
Subject/Key Words:
Data Analysis, Differential Item Functioning (DIF), Graphical Analysis, Item Response Theory (IRT)


The detection of differential item functioning (DIF) has become an important psychometric research topic in recent years. A number of item response theory (IRT) methods for solving this problem have been suggested. A common approach is to calculate some function of the area between item response curves estimated from the subpopulations of interest. While these methods relay overall item level DIF information, they do not indicate the location and magnitude of DIF along the ability continuum. In order to provide these important details, this paper presents a method for producing simultaneous confidence bands for the difference between item response curves. After these bands have been plotted, the size and regions of DIF are easily identified. Implementation considerations and illustrative examples are also given. (21pp.)

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