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From |
Maarten buis <maartenbuis@yahoo.co.uk> |

To |
stata list <statalist@hsphsun2.harvard.edu> |

Subject |
st: RE: xtmelogit questions , thanks! |

Date |
Fri, 7 Jan 2011 08:43:49 +0000 (GMT) |

--- Zhang Libin wrote me privately: > I happened find your answer on ifference between xtlogit, xtmelogit, > gllamm at http://www.stata.com/statalist/archive/2010-12/msg00558.html. > My dissertation is a 3-level model on binary outcome (obesity or not), > and I'm using stata for programming. > > Level 1: individual sociodemographic factors; diet, physical activity. > (N=9000) > > Level 2: community factors; (N=200) > > Level 3: Gini coefficient in 9 different states. (N=9) > > Since there are only 9 provinces, I'll keep the level 3 as fixed effects. > > 1. How can I turn the three level model into two level model by using > xtmelogit? Meanwhile I still need GINI in the model. Can I do that? > > 2. I am not familiar with xtmelogit. Could you give me any sample codes > so that I can figure out where to put the ID variables if STATA needs ID > variable as SAS do? The idea behind statalist is that you do not contact its members privately as is discussed in the statalist FAQ: <http://www.stata.com/support/faqs/res/statalist.html#private> Regarding your first question: I suspect that with fixed effects you mean adding dummies for countries. This is a fixed effects estimator if your model were linear, but in non-linear models that is no longer true. You can find an explanation of this point (for the case of ordered logit) here: <http://www.stata.com/statalist/archive/2003-09/msg00103.html> They also make the point that if your samples whithin each country is large enough so that you would be comfortable to publish analyses on each country sub-sample seperately, then adding dummies should work reasonably well. I guess that is the case for your study, but I would avoid the term "fixed efects" and instead say that you added country dummies. You can add gini coefficients and country dummies if each country is observed multiple times (e.g. multiple years) and the gini changes enough within a country from year to year. If you only have data for one year or if the gini score in one year is very close to the gini score in the next year for the same country, then you can't add both to your model. Regarding your second question: The manual contains a nice sequence of examples where they gradually go from simple to more complex models. hope this helps, Maarten -------------------------- Maarten L. Buis Institut fuer Soziologie Universitaet Tuebingen Wilhelmstrasse 36 72074 Tuebingen Germany http://www.maartenbuis.nl -------------------------- * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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