

MIMIC model for DIF detection 

Message/Author 


Dear Dr.Muthen, I played with the MIMIC model for DIF detection and found that the results from significance test of the coefficient for grouping variable on the studied item and the chisquare test for nested model comparison (i.e., No DIF vs DIF models) are different. For example, model comparison suggested that DIF occurs in an item but the coefficient of grouping variable on that item is not statistically significant. Here's the command I used for DIF model. MODEL: ability BY i1i20; ability ON group; i7 ON group; !uniform DIF For No DIF model, the last line was deleted. Is it possible that two approaches (sig. test and nested model comparison) result in different ways? If so, which one should be used? Thank you 


I think rather than deleting the last line, you need to specify: i7 ON group@0; 


I think another question has arisen. I tried to run No DIF model by (1) deleting the "i7 ON group;" line and (2) constraining the parameter "i7 ON group@0;" as you suggested. Here's the result: (1) ChiSquare Test of Model Fit Value 304.999 Degrees of Freedom 21 PValue 0.0000 Loglikelihood H0 Value 1123.327 H1 Value 970.828 Information Criteria Number of Free Parameters 21 (2) ChiSquare Test of Model Fit Value 304.999 Degrees of Freedom 21 PValue 0.0000 Loglikelihood H0 Value 1123.327 H1 Value 970.828 Information Criteria Number of Free Parameters 21 What is the difference I should expect from using "@0" instead of deleting the command line? And how using "@0" can explain the different results between the significance test and model comparison that I've asked in previous post? Thank you so much, 


If that makes no difference, I would need to see the relevant outputs and your license number at support@statmodel.com. 

Back to top 

