I am trying to determine differences in growth trajectory for three predefined groups. I have a working Launch Model and there is a significant group effect on the slope and frailty factors. I wanted to test differences between groups using one group as the comparison group. You can see that I have defined one group as the contrast group in the define statement. However, Mplus stops me from running this analysis due to missing values. However, this is exactly what I am testing and this is how a two-part model is set up. A large number of cases WILL be missing. What is the proper procedure here??
*** ERROR One or more variables in the data set have no non-missing values. Check your data and format statement.