I want to do the kind of analysis that is in ex 9.16. However, my data is already in LONG form and already has ID and repetition variables. How can I let Mplus know about those variables without doing the WIDETOLONG transformation and having Mplus construct them as I do not need it to do so? When I simply choose cluster and within variables using the variables already in the data set, I get the error that there is variation within clusters. I suspect this is because it is not understanding that we've got repeated measures. So I suppose the problem is not with the ID variable but with picking out the repetition variable that I already have in the data set. Again, I do not need Mplus to construct this variable. I just need Mplus to recognize that there is a special (repetition) variable in the data set and that the data is already in LONG format. Alternatively, I would be happy to do the analysis at a single level with time as a covariate but the RANDOM analysis option seems to work better with TWOLEVELS than not. I do not know why. But perhaps that's a question for another day. I appreciate any help.