I am quite confused at the moment regarding multilevel models as implemented in SAS PROC MIXED. I am new to mixed models.
Let's say I have 2 treatments, a new treatment and a control. And let's say that I have a sample of n subjects, each is contributing 1, 2 or 3 samples, i.e., the treatment (new or control) is being applied in 1 to 3 places in the subject's body.
I can't understand the difference between:
Proc mixed data=... class Treatment SubjectID; model Y = Treatment; Random SubjectID; run;
Proc mixed data=... class Treatment SubjectID; model Y = Treatment; Random intercept / subject = SubjectID; run;
I can't figure out this intercept / slope issue and its meaning.