PROC NLMIXED

[Carl190]

Hi all.

My data is a 3-level data (level 1: repeated measures, level 2: patients, level 3: clinics).

I wonder if PROC NLMIXED can be used for 3-level data.

I am getting conflicting answers to this.

Thanks in advance for your help.

Carl

[lvm]

Because there is only one allowed RANDOM statement with one SUBJECT option, many people think that NLMIXED is only for 2-level hierarchies. But if you understand variance-covariance matrices, one can force NLMIXED to fit multiple-hierarchy models to data. This is tricky, requiring a lot of coding. It is not the type of thing that can be simply written out here (at least for me). Example 15.4 in Littell et al. (2006; SAS for Mixed Modell, 2nd edition) deals with this explicitly. You can buy this for SAS Press or Amazon (etc.).

[Carl190]

I got this book, I will check the example.

Thanks for your suggestion,
Carl.