I wish to test for differential item functioning (DIF) using MIMIC method for the following multilevel model.
ESTIMATOR = WLSMV; TYPE = TWOLEVEL; Items are treated as categorical; Model = same 3 factor model at within- and between-levels (each factor reflected by 4 items); Casual Indicator and possible DIF source is a continuous single indicator variable;
As I understand it thresholds may only be estimated at the between-level for this model and that with categorical data DIF refers to prediction of thresholds across levels of the DIF source which is my case is a continuous single indicator variable.
How would uniform DIF manifest itself in such a model? Would we look for differences in item thresholds in two different models 1) the first model with each item being regressed onto the DIF source and 2) without the item being regressed onto the DIF source? And if the thresholds were different in each model how would they be compared?