Re: How do I perform generalized estimating equation for clustered data in SPSS?

Posted by Andy W on
URL: http://spssx-discussion.165.s1.nabble.com/How-do-I-perform-generalized-estimating-equation-for-clustered-data-in-SPSS-tp5740704p5740708.html

Lot of questions, I will get to the final two as I can kind of answer them quickly.

(1) what is the actual role of the Subject and within subject in the "Repeated" section in GEE? What if I entered individual ID variable instead of school ID variable?

This allows the errors in the model between individuals within schools to be correlated with each other. Since you don't have repeated measures for an individual person, if you used as a person ID there is nothing to correlate to. This would make sense if you have multiple test scores per person and stacked the equation (e.g. one for math and one for writing, etc.)

(2) GEE model itself automatically controls for cluster effect (by selecting "robust estimator"), is it correct? If it's correct, why we need to enter "school" as a repeated subject?

When people say robust it can mean different things. I thought the COV=ROBUST option was for heteroskedastic robust covariance matrices in SPSS. Advocates for GEE say the procedure is generally robust to misspecification of the error covariances as long as the mean equation is correct. So those are two different things.

For the others I prefer to just specify the equation at the start I want to sue (I don't put much into the metrics to choose model A over Model B). Given the interaction model is more flexible I would just go with that (if there are no differences it will show). The split file approach has less power than pooling the models (it would be closer to equivalent to having country interaction effects for each right hand side variable), so I wouldn't prefer that either.