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st: RE: Non-linear multilevel modeling


From   "Feiveson, Alan H. (JSC-SK311)" <alan.h.feiveson@nasa.gov>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Non-linear multilevel modeling
Date   Wed, 7 Dec 2011 12:11:21 -0600

Jennyfer - By "nonlinear" do you mean non-normally distributed, a nonlinear trend (or both)? You can often model a non-linear trend by using simple functions of the predictor as additional predictors - e.g. time and time^2 and still use -xtmixed-. If your data is percentages with known counts and you want to model it that way with two levels, you could use -xtgee- with a binomial family. For three levels, though this could be a problem. Still if most of the variability is between regions, -xtgee- with regions as your grouping variable might be a reasonable approach. 

Al Feiveson

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Jennyfer Wolf
Sent: Wednesday, December 07, 2011 10:42 AM
To: statalist@hsphsun2.harvard.edu
Subject: st: Non-linear multilevel modeling

Dear Statalist,

which options are there to do non-linear multilevel modelling in Stata?
My dependent variable is a percentage and I have only one independent
variable which is time.
My different levels are regions and countries.

For the moment I just have a model for a linear relationship:

xtmixed depvar year || region: || country:

Thank you very much for your answer.
Jennyfer
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