For analysis of an intervention effect (RCT) I am using a LGM with different moderators that might affect the slope. One of these is number of sessions a participant attended, which is 0 for all participants in the control condition. Therefore I used "condition" ad grouping variable and specified the model for both groups separately: not using the number of sessions in the control group. However, I still get this error when I try to run the syntax: *** ERROR One or more variables have a variance of zero. Check your data and format statement.
Maybe I am overlooking something. Thank you in advance for your help.