Dear all,    I am investigating subjective stress levels during a psychosocial stress test. I ran into problems with a more complex model, and started with simplifying my model to figure out the source of the issues. I am already running into trouble by adding a quadratic term of time.    My code is as follows:    proc mixed data=MAST_long_VAS; class PPID Time; model BC_stress = Time Time*Time / solution residual influence; repeated Time / subject=PPID type=ar(1); run;   This model runs without any problems or warnings, but does not give me the output for the fixed effect of Time*Time (only the fixed effect of Time). I tried removing "Time" from the class statement, but then I get the warning that only class variables are allowed in the repeated statement. Can anyone help me with this?    Thanks in advance!  ... View more