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Re: AW: st: table of deviance after multiple regression!

From   Maarten buis <>
Subject   Re: AW: st: table of deviance after multiple regression!
Date   Tue, 1 Jul 2008 16:09:09 +0100 (BST)

--- Heckendorn Felix <> wrote:
> The problem in fact might appear simple. I have an experiment with 3
> different treatments (one of which is the control treatment). The
> response variable follows a negative binomial distribution.
> The experiment was conducted at 6 different sites which gives us 6
> replicates (n=6).
> What I ultimately want to know is:
> 1. how much better is my treatment 1 and 2 when compared to the
> control.
> 2. is there a significant influence of the experimental sites.
> I recoded my treatments and have set the control treatment to 0. My
> model then consists of my response and two explanatories (i)
> treatment and (ii) experimental site. With the gnbreg command I get
> coefficients for the 2 treatments and for 5 experimental sites (one
> site omitted). If I want to know whether experimental site as such is
> an important variable for the model, I need to check the model with
> and without the variable 'experimental sit'. Apparently the residual
> deviance D allows an answer to that question. How to do?  

This is implemented as the likelihood ratio test, see -help lrtest-.
Alternatively you can do the Wald test, see -help test-.

-- Maarten

Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434

+31 20 5986715

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