Measuring differential item and test functioning across academic disciplines

Language Testing in Asia

Table 2 Items with DIFAcross all groups*

*Person class*	*Summary DIF Chi-square*	*D.F.*	*Prob.*	*Between-Class Mean-Square*	*Item T=ZSTD*	*Item number*
5	10.2878	4	0.0357	0.5532	-0.5242	5

*The first column, Person Class is the count of groups (in this case, major) with estimable DIF for the item. The Summary DIF Chi-Square column is the sum of the squared normalized t-statistic value for each item. D.F. represents the degrees of freedom or the count of majors minus 1 contributing to the chi-square. The Prob. is the probability of the chi-square (any value under 0.05 is statistically significant) followed by the Between-Class Mean-Square. The sixth column, the Item T=ZSTD represents the significance of the Mean-Square standardized as a unit-normal deviate (t-statistic with infinite degrees of freedom). The final column, the item number, accords with the question number on the test.