Wyse Adam E
Michigan Department of Education, Bureau of Assessment and Accountability, 1813 Chatham Ave., Arden Hills, MN 55112, USA.
J Appl Meas. 2013;14(2):118-28.
Differential item functioning (DIF) cancellation occurs when the cumulative effect of an item or set of items exhibiting DIF against one subgroup cancels with other items that exhibit DIF against the comparison group and hence results in non-existent DIF at the test level. This paper investigates DIF cancellation in the context of Rasch measurement. It is shown that this phenomenon is not a property of the Rasch model, but rather, a function of the manner in which item parameters are estimated and the way that DIF impacts these estimates. The conditions under which DIF cancellation would exist when using the Rasch model are suggested and a proof is provided to support this suggestion. Empirical examples are provided to refute prior suggestions that DIF cancellation always exists if the Rasch model is used.
当一个项目或一组项目对一个亚组表现出差异项目功能（DIF）的累积效应与对对照组表现出DIF的其他项目相互抵消，从而在测试层面导致不存在DIF时，就会发生DIF抵消。本文在拉施测量的背景下研究DIF抵消。结果表明，这种现象不是拉施模型的一个属性，而是项目参数估计方式以及DIF影响这些估计的方式的一个函数。文中提出了使用拉施模型时DIF抵消存在的条件，并提供了一个证明来支持这一建议。还提供了实证例子来反驳之前关于如果使用拉施模型DIF抵消就总是存在的建议。
