I am currently writing a paper comparing various packages in  
different programs, and how they handle GEE. I was wondering if you  
could help me out a bit.
Beyond the options included in each package, I've noticed a variance  
in the various estimates and standard errors for most working  
correlation options between packages. The most is observed in  
Unstructured, and none in independence obviously. From what I've been  
able to gather the difference is coming from how the working  
correlations are calculated. Slight modifications in the residual  
calculation etc.
I was wondering if you could tell me how geepack or gee calculates  
correlation, and how I could reproduce the working correlation in  
geepack, without using GEE, so I can see the difference. Or at least  
the initial iteration correlation estimate.
Any information you know about other packages would be greatly  
appreciated too!!
Could you also include full citation for yourself so I can properly  
cite you,

Cameron Redsell-Montgomerie
MSc Statistics
University of Guelph
MACN rm:501
credsell@uoguelph.ca





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