Hello,

 

I am trying to analyse data from a longitudinal study using PROC MIXED in SAS software.

This is a multicentre trial and therefore, I was thinking to specify the subject variable in the REPEATED statemet with an autoregressive AR(1) covariance matrix and to include a variable City in the RANDOM statement to assess its importance by likelihood ratio.

I would be grateful for any suggestions related to the covariance matrix and whether including City in the RANDOM statement is a good approach or if there are other alternatives.

 

Thank you and best regards,

Oscar.