Hello experts,

In FMM (finite mixture models), our main models(s) could have certain IVs. Then, I can add some variables to lcprob to specify variables that determine the probabality of being in each class. For example, Stata help document says that total medical expenditure (DV) could be predicted by gender, age, and income. In a basic model, it only uses the mentioned IVs. Later, it says, with that, we are assuming that prior probability of being in each class was the same among all individuals. However, it would make a better sense if include "total number of chronic issues" each person has in "lcprob" part of the model.

Now, my question is: what is the criteria on the basis of which we decide one variable should be in the main model rather than in lcprob part of the model? In other words, in the mentioned example" total number of chronic issues" could have been used as one of the IVs in the model.

I hope my question is clear.

Thanks in advance