I'm conducting a MLM analysis using proc mixed. The level 1 variables are dummy coded variables for grade comparisons (Dummy_FS=freshmen vs seniors; Dummy_SS= sophomores vs seniors; Dummy_JS = juniors versus seniors). Note that some institutions do not have freshmen, others do not have sophomores and others do not have juniors. I requested the solutions for random effects and for some institutions I got zero estimates for some of the dummy variables. Those zero estimates correspond to those institutions that do not have information available to compute those estimates. For example, looking at the attached table, Institution 372 do not have juniors nor sophomores, hence the zero estimates in Dummy_FS and Dummy_SS. My question is: what does the zero estimate mean? Specifically, I'd like to know if those institutions with no information in specific comparisons, are being considered in the overall estimation of the random slopes or if they are not being considered in the estimation. How should I interpret the zero estimates and the standard error of prediction for those institutions?
... View more