Hi, I run a mixed model for a repeated mesures analysis. I have 2 factors : group factor with 4 levels and week factor with 5 levels. I want to test the time effect in each group and the group effect in each week.   I used the following code to test time effect in group 1 and group effect in week 2 :    proc mixed data=rawdata; class mice group week; model col1 =  group week week*groupe ; repeated / subject=mice type=cs;   contrast "Time effect in group 1"  week -1 0 0 0 1 groupe*week -1 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0, week 0 -1 0 0 1 groupe*week 0 -1 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0, week 0 0 -1 0 1 groupe*week 0 0 -1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0, week 0 0 0 -1 1 groupe*week 0 0 0 -1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0;   contrast "Group effect at time 2"      group -1 0 0  1 week*group 0 0 0 0 -1 0  0 1 0 0 0 0 0 0 0 0 0 0 0 0,     group 0 -1 0  1 week*group 0 0 0 0 0 -1  0 1 0 0 0 0 0 0 0 0 0 0 0 0,     group 0  0 -1 1 week*group 0 0 0 0 0  0 -1 1 0 0 0 0 0 0 0 0 0 0 0 0; run; It is working for "Time effect in group 1" but it does not work for "Group effect at time 2". In the log, I can see " the contrast is not estimable".   Please, can you let me know if my first contrast is correct and if so, why the second one does not work? Many thanks Matthieu   ... View more