I have applied the BLRT to help me deciding the number of classes in a traditional latent class model. But what happens when this test is applied to a model with restrictions? More concrete then I have assumed the conditional probability for a certain answer to an item to be equal among some classes. M-plus do not give any errors, but I am not sure what the alternative model is. Is it the model with k-1 classes without any restrictions or Ö ?
Thank you for your answer. It gave me a couple of ideas that I have now tried out. My problem is that maybe it is not clear which restriction there is left on a k-1 class model, when there are parameter restrictions across classes. One of my k class models looks like this:
I have tried fitting this model switching around the classes, and the BLRT and itís DF changes. In this example the BLRT only has one degree of freedom. My guess is that this is because the two-class model with class 2 and class 3 does not have any restrictions when class 1 is erased. Is it correct that Mplus always try to remove the first class? If so it is very nice, because then I can control the restrictions in my k-1 alternative model.
Alternatively, is there a way to directly specify the k-1 class model? This is relevant for me, as I have more complicated parameter restrictions across classes for the piís.