Andrich David, Hagquist Curt
The University of Western Australia, Crawley, Western Australia, Australia.
Karlstad University, Karlstad, Sweden.
Educ Psychol Meas. 2015 Apr;75(2):185-207. doi: 10.1177/0013164414534258. Epub 2014 May 16.
Differential item functioning (DIF) for an item between two groups is present if, for the same person location on a variable, persons from different groups have different expected values for their responses. Applying only to dichotomously scored items in the popular Mantel-Haenszel (MH) method for detecting DIF in which persons are classified by their total scores on an instrument, Andrich and Hagquist articulated the concept of artificial DIF and showed that as an artifact of the MH method, real DIF in one item favoring one group inevitably induces artificial DIF favoring the other group in all other items. Using the dichotomous Rasch model in which the total score for a person is a sufficient statistic, and therefore justifies classifying persons by their total scores, Andrich and Hagquist showed that to distinguish between real and artificial DIF in an item identified by the MH method, a sequential procedure for resolving items is implied. Using the polytomous Rasch model, this article generalizes the concept of artificial DIF to polytomous items, in which multiple item parameters play a role. The article shows that the same principle of resolving items sequentially as with dichotomous items applies also to distinguishing between real and artificial DIF with polytomous items. A real example and a small simulated example that parallels the real example are used illustratively.
如果对于同一变量上处于相同位置的人,来自不同组的人对其回答有不同的期望值,那么该项目在两组之间就存在差异项目功能(DIF)。在用于检测DIF的流行的Mantel-Haenszel(MH)方法中,仅适用于二分计分项目,其中人员根据其在一种工具上的总分进行分类,安德里奇和哈格奎斯特阐述了人为DIF的概念,并表明作为MH方法的一种人为现象,一个项目中有利于一组的真实DIF不可避免地会在所有其他项目中诱导出有利于另一组的人为DIF。使用二分Rasch模型,其中一个人的总分是一个充分统计量,因此证明可以根据总分对人员进行分类,安德里奇和哈格奎斯特表明,为了区分由MH方法识别出的项目中的真实DIF和人为DIF,隐含了一种解决项目的顺序程序。本文使用多分类Rasch模型,将人为DIF的概念推广到多分类项目,其中多个项目参数起作用。本文表明,与二分项目一样,顺序解决项目的相同原则也适用于区分多分类项目中的真实DIF和人为DIF。文中使用了一个真实例子和一个与真实例子类似的小型模拟例子进行说明。