Hello,
I have a dataset with a continuous outcome variable and 3 treatments (1 of which is placebo). I have about 60 observations in my dataset; 60 subjects each of which got 1 treatment and was measured once - the dataset is balanced but measurements were taken in blocks of days but only 2 measurements were taken each day (incomplete blocks?). I need to include the block in my model as a random effect. I am trying to get the effect of the drug and im running a proc mixed with a random block effect, but i am not getting an anova table and am getting an error that the "Estimated G matrix is not positive definite." Can anyone tell me what I am doing wrong? Thank you.
Please share your PROC MIXED code and enough of your data to enable some trouble shooting. I suspect that you may have misspecified the random effect, as the message 'Estimated G matrix is not positive definite' means that at least one variance parameter is being set to zero. There are a couple of ways around this, but it depends on design, data structure and code.
Steve Denham
Are you ready for the spotlight? We're accepting content ideas for SAS Innovate 2025 to be held May 6-9 in Orlando, FL. The call is open until September 16. Read more here about why you should contribute and what is in it for you!
Learn the difference between classical and Bayesian statistical approaches and see a few PROC examples to perform Bayesian analysis in this video.
Find more tutorials on the SAS Users YouTube channel.
Select SAS Training centers are offering in-person courses. View upcoming courses for: