full and reduced Cox model with cluster

["Sylvie Dallot" <sdallot@ushrl.ars.usda.gov>]

 Hello all,

I want to use a Cox model with the cluster(group) term. How can I test the 
difference between a full and a reduced Cox models with a cluster term ? I 
guess that the usual LR test is not correct in this case.
Can I use instead the differences between the wald tests ? 

Thanks for your help

Sylvie DALLOT
USDA/ARS/USHRL
2001 South Rock Road
FORT PIERCE, FL 34945
USA
phone: 1 772 462 58 60
FAX: 1 772 462 59 86