Reference : Angoff’s Delta method revisited: improving the DIF detection under small samples
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Mathematics
Angoff’s Delta method revisited: improving the DIF detection under small samples
Magis, David mailto [Université de Liège - ULiège > Département de mathématique > Statistique mathématique >]
Facon, Bruno [ > > ]
British Journal of Mathematical & Statistical Psychology
British Psychological Society
Yes (verified by ORBi)
United Kingdom
[en] Differential item functioning ; Delta plot ; transformed item difficulties ; item analysis ; small samples
[en] Most of the methods for detecting differential item functioning (DIF) are suitable when the sample sizes are sufficiently large to validate the null statistical distributions. There is no guarantee, however, that they still perform adequately when there are few respondents in the focal group or in both the reference and the focal group. Angoff’s Delta plot is a potentially useful alternative for small-sample DIF investigation, but it suffers from improper DIF flagging criterion. The purpose of this paper is to improve this classification rule under mild statistical assumptions. This improvement yields a modified Delta plot with an adjusted DIF flagging criterion for small samples. A simulation study was conducted to compare the modified Delta plot to both the classical Delta plot approach and the Mantel-Haenszel method. It is concluded that the modified Delta plot is consistently less conservative and more powerful than the usual Delta plot, and is also less conservative and more powerful than the Mantel-Haenszel method as long as at least one group of respondents is small.

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