If my theory makes specific hypotheses about trajectory groups, can I put in the model specifications apriori and then test them against an unrestricted model? I tried this and failed miserably, and I'm not sure why - if my model specifications were written incorrectly, if what I tried to do is impossible, or if the model really didn't fit.
I was trying to replicate someone else's findings with my data. Guo et al (2002) found a 4 group model for marijuana use trajectories: (1) early high, (2) escalator, (3) late onsetter, (4) nonuser. I tried to replicate these group patterns by using model constraints.
First I labeled all the parameters I wanted to constrain: