Thank you Thomas,
 if i understand what you say below i need to use glm in order to have the
deviance and consider it for the model with svyglm and choose the best
model. I use  glm and svyglm for two models but don't have deviance for the
svyglm. As i need to choose with the two models it is correct to use the
deviance from glm model for the svyglm.
Regards.

2010/7/31 Thomas Lumley <tlumley@u.washington.edu>

> On Sat, 31 Jul 2010, aline uwimana wrote:
>
>  This message is for those familiar with the survey package. I need to do
>> regression logistic and choose the best model which explain the impact of
>> the
>> indepndent variables by using AIC,BIC,...
>>
>> > sum.coef<-summary(svyglm(y~x1+x2+x3, design=design,
>> family=quasibinomial(), data=data))$deviance
>>
>>  is this the correct way for obtaining the deviance.
>>
>
>
> You can use the deviance() function to get a number.  This number isn't
> really the deviance, because svyglm() doesn't use maximum likelihood
> estimation. It doesn't have a chi-squared distribution, for example.  It is
> the deviance that would be computed if the weights were precision weights
> and were rescaled to sum to the sample size. There isn't a real deviance.
>
> The reason this number is reported is that, although differences in
> deviance do not have a chi-squared distribution, they do asymptotically have
> a known distribution and this gives the Rao-Scott 'working deviance' tests.
> These tests are widely used for loglinear models but also apply to
> generalized linear models and the Cox model. The function regTermTest() does
> Rao-Scott tests with the method="LRT" option.
>
>   -thomas
>
> Thomas Lumley
> Professor of Biostatistics
> University of Washington, Seattle
>

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