This study evaluated the robustness of DIF detection for multidimensional polytomous items using two different estimation methods, MG-CFA and MGRM-DFIT. A simulation study across 960 study conditions was performed. The purpose of this study was to establish the Type-I error rate and Power of DIF detection for the MG-CFA and MGRM-DFIT estimation methods across the study conditions. The MGRM-DFIT method consistently controlled Type-I error rate under alpha across all study conditions. Though the MGRM-DFIT method demonstrated high power in detecting DIF for the combined items, it had lower power in detecting DIF for each item individually. The MGRM-DFIT method had higher power of DIF detection when impact (true distributional differences) is in the opposite direction of manipulated DIF. Overall, compared to the non-DIF items, NCDIF values are larger, and CDIF values are smaller for the 4 DIF items. Across the replications and the study conditions, CDIF was not as consistent as NCDIF. The MG-CFA method demonstrated slightly inflated Type-I error rate in a couple of study conditions (particularly in the presence of impact). However, the MG-CFA method demonstrated lower power across all study conditions. This could partly be explained by the low magnitude of DIF that was manipulated in the 'α/λ' parameter in this study. Parameter estimation for the MGRM, and the MGRM-DFIT method should be incorporated as part of commonly used software packages. In general, the MG-CFA method is recommended for DIF detection with multidimensional polytomous types of items, since it performs more consistently as a univariate test and as a multivariate test, and is easily available as part of several commonly used software packages.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-04182011-000321 |
| Date | 13 May 2011 |
| Creators | Kannan, Priya |
| Contributors | Dr. Kevin H. Kim, Dr. Levent Kirisci, Dr. Suzanne Lane, Dr. Clement Stone |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-04182011-000321/ |
| Rights | restricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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