I am conducting a multilevel CFA and would like to test for structural invariance in my measure across two time points. The data set includes observations of therapists on an 11 item scale at two time points. Not all of the therapists are represented at both time points.
I have been able to get the multilevel CFA to run. However, when I try to add in time (pre- or post-treatment) with the Grouping statement to test for measurement invariance I receive an error message:
*** ERROR Cluster ID cannot appear in more than one group.