Goodness of fit (QIC) in Generalized Estimating Equations (GEE)

#1
Hi,

I have a question concerning goodness of fit which is measured as QIC in the GEE analysis:

In general I learned that if QIC decreases the change in the model was for the better. => Decrease in QIC = Good

However, I am trying to add new model terms and for all of them QIC increases. Is QIC only decreasing when there is a change in the structure of the working correlation matrix or as well if I add model terms.

Does anybody find my mistake ?

Thank you
Laura