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Re: st: gllamm and weight


From   ubuntu acdc <ubuntu.acdc@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: gllamm and weight
Date   Mon, 6 May 2013 09:30:26 +0200

Thank you very much Steve for your response and your help.

Best regards

Lionel

2013/4/26 Steve Samuels <sjsamuels@gmail.com>:
>
> Lionel:
>
> Five countries is not enough for a random-effects analysis or for
> inference based on countries as clusters (e.g. Moineddin et al., 2007)
> A random-effects analysis is also questionable because of the
> non-random selection of countries: what population would an estimated
> between-country variance component describe?
>
> So treat countries as fixed factors; you won't need -gllamm-. If
> individuals were selected in sample surveys, you can use -svy:logit-
> with countries as design strata as well as analysis factors.
> otherwise plain -logit- will do
> .
> Reference:
>
> Moineddin, Rahim, Flora Matheson, and Richard Glazier. 2007. A simulation study of sample size for multilevel logistic regression models. BMC Medical Research Methodology 7, no. 1: 34. https://www.biomedcentral.com/1471-2288/7/34)
>
> Steve
>
>
> Dear stata users,
>
> I have some questions about gllamm and multilevel model with weight
> and any help about it will be appreciated. First, to better
> understand, I describe my analysis. We have realized a survey in 5
> countries (countries have not been choosen randomly). In each country,
> 300 people have responded to survey and in each country, to insure
> that the results were representative of the target population, the
> data were weighted according to age, gender. Until now, I have studied
> each database separatly. Today, I have merged the five database to
> obtain  a weighting single database of 1500 people. I would like to
> study a binary outcome so I think a multilevel logistic regression is
> the most appropriated. There are two levels : first is individual and
> second is country. So I try to use xtlogit but unfortunately, I can't
> use weight. So I look for gllamm and it seems possible to use weight.
> The syntax code is :
> gllamm outcome explanatory_variables, i(country) fam(binom)
> link(logit) nip(30) pweight(poids)
>
> I read help about gllamm and I see there are two sort of weights :
> pweight (just for individuals) and weight (but integer are required).
> So I think, in my analysis, i must use "pweight". I have to be careful
> with suffix option (in my database weight is named "poids1" so in the
> stata syntax i just write "poids"). I have no weight for level 2 i.e
> country. So, if I well understand, automatically a weight of 1 is
> created. I also read there might be a problem about rescaling for
> weight and I read the paper of Rabe-Hesketh (2006) about it but I am
> not sure to have understood everything.
>
> So, to be sure that I don't make some mistakes about weight use,
> syntax, methodology etc..., I post it on statalist. Any help would be
> greatly appreciated.
>
> Thank you very much for your response and sorry for my english (I'm french...).
>
> Lionel FUGON
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