To control Type I error rates in assessing differential item functioning, constant item (CI) method was proposed in literature. The performance of CI method was found highly correlated to the anchor items. The strategy to select several items as anchor first and then assessing DIF for other items in the test was called DIF-free-then-DIF strategy (DFTD; Wang, 2008). It was found the more DIF-free items in the anchor test, the better performance of DFTD strategy. However, in Wang and Shih (2010), the anchor items were DIF-free by design. To implement the DFTD strategy into practice, the anchor should be selected and the performance of DFTD strategy can be better assessed with the selected anchor. In this study, the performance of DFTD strategy was assessed in the MIMIC method through simulation study. Four independent variables were included in this study: sample size, percentage of DIF items in the test, DIF assessment method, and anchor item selection method. Our findings and conclusions will be given in details in the presentation.
|Publication status||Published - Jul 2011|