Fig. 2
From: Investigating item complexity as a source of cross-national DIF in TIMSS math and science
ICCs When Fitting 2PL and LPE to the Studied Item, 4th Grade Math, TIMSS 2011. For Item M031016, the NCDIF index decreases from 0.964 to 0.094 when fitting with 2PL versus LPE having \(\xi =15\), while the changes in RMSD are from 0.023 to 0.018 for the low proficiency country group, and from 0.036 to 0.017 for the high proficiency country group. For Item M031218, the NCDIF index reduces from 0.464 to 0.056 when fitting 2PL versus LPE having \(\xi =0.2\), while the changes in RMSD, are from 0.041 to 0.025 for the low proficiency country group, and from 0.019 to 0.018 for the high proficiency country group