Hi everyone, I have a question about proc mixed procedure with some missing outcome values. using same dataset, same model, the two code have the same number of "Number of Observations Used", but very different parameter estimates. I suppose these estimates should be the same. Could anyone help explain why these estimates are different?  Thank you in advance!   code1: proc mixed data = mydata; class id order(ref="0"); model MS=order group stability /s ; repeated / type=un subject=id r rcorr; run;     Code2 (this code returns the same results as using the where statements in a data step to subset mydata, i.e.. data mydata;set mydata;where MS ne .;run; proc mixed data=mydata;...) proc mixed data = mydata; class id order(ref="0"); model MS=order group stability /s ; repeated / type=un subject=id r rcorr; where MS ne .; run;        ... View more