I have data from population based observation (not questionnaires but yearly observation from secondary database) and I already have a common model for each populations (6 groups, each has the same latent variables, observed variables, and the structural models are also the same shape). As the study is some kind of longitudinal basis (not independent to each other), am I still be able too use MGA (Multi Group Analysis)? My result does not pass the MICOM procedure, is doing a MICOM procedure an obligatory prior MGA in my specific case?