Abstract :
[en] This paper focuses on the identification of differential item functioning (DIF) when more than two groups of examinees are considered. We propose to consider items as elements of a multivariate space, where DIF items are outlying elements. Following this approach, the situation of multiple groups is a quite natural case. A robust statistics technique is proposed to identify DIF items as outliers in the multivariate space. For low dimensionalities, up to two three groups, also a simple graphical tool is derived. We illustrate our approach with a re-analysis of data from Kim, Cohen, and Park (1995) on using calculators for a mathematics test.
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