Hm, I don't follow. Your original question was: I find that the Estimate of time is the same in IV1, IV2 and IV3, but the Estimates of IVs are changed. Is that normal? I took this question to mean you were referring to the estimates of the fixed effects of IV and time (the rest of what I write is predicated on that). But, then you typed this: I had the confusion because I would expect an interaction between the IV and the time. That's why I was surprised when the coefficient of time remained consistent. However, I could not add the IV*time term because both of them are continuous variables. There is no restriction on interactions among continuous variables in generalized linear models; there is no problem with adding a continuous*continuous term as a fixed effect. Are you trying to put this effect in the REPEATED line, by chance (I cannot see *why* you'd do that, but it would throw the error that only class level variables are allowed).
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