PROC MIXED: The covariance of difference between two groups

[pengznuc]

May you please help me understand how I could get cov(1,2)  for difference between 2 groups in proc mixed? I looked at the book "SAS for Mixed Models, 2nd Edition, by R. Littell et al. (SAS Press)" but still I do not find the answer.

In diffs output, only estimate and stderr included, but not covariance.

Thanks

[SteveDenham]

I think using the COVB option in the MODEL will give you what you want.

SteveDenham