I've restructured longitudinal data from 3 waves of repeated measures to 5 grade repeated measures as per Bollen and Curran's (2006) synthetic cohort approach. I have been successful using this approach with two separate outcome variables so far, but am having trouble with a third separate outcome variable. When I try to run the model MPlus is detecting data where there should not be any (i.e., where the covariance coverage should be zero). I have checked the data set and tried recreating the .csv data file from scratch in case something went wrong in the conversion process. None of this seems to have worked, however, and I was wondering what else might be going wrong that the covariance coverage is incorrect. Any help would be much appreciated -- thank you for your time!
I have a question regarding obtaining a negative variance in my growth factor.
I am studying the change of kids' diabetes adherence overtime. When i fitted a univariate growth model for the repeated measures, the model fit was fine and there is no negative variance for the growth factor. However, once i include other predictors in my model, i obtained negative variance for the growth factor. I wonder if this could be due to the fact that the is lack of variability in the diabetes adherence growth factor?