[R-sig-eco] GEE and AIC

[ONKELINX, Thierry]

Brianne,

GEE is based on asymptotic approximations. Therefore it will only yield
valid parameter estimate if you sample size is larger enough. So I would
not rely on GEE if the sample size is smaller than 80.

HTH,

Thierry


------------------------------------------------------------------------
----
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature
and Forest
Cel biometrie, methodologie en kwaliteitszorg / Section biometrics,
methodology and quality assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium 
tel. + 32 54/436 185
Thierry.Onkelinx at inbo.be 
www.inbo.be 

To call in the statistician after the experiment is done may be no more
than asking him to perform a post-mortem examination: he may be able to
say what the experiment died of.
~ Sir Ronald Aylmer Fisher

The plural of anecdote is not data.
~ Roger Brinner

The combination of some data and an aching desire for an answer does not
ensure that a reasonable answer can be extracted from a given body of
data.
~ John Tukey

-----Oorspronkelijk bericht-----
Van: r-sig-ecology-bounces at r-project.org
[mailto:r-sig-ecology-bounces at r-project.org] Namens BriAnne Addison
Verzonden: vrijdag 30 mei 2008 0:51
Aan: r-sig-ecology at r-project.org
Onderwerp: [R-sig-eco] GEE and AIC

This is tangential to the previous string.

Has anyone calculated (pseudo)AIC values for generalized estimation 
equations in the GEE package (or related packages)?  I wish to compare 
among several models where the data are not phylogenetically 
independent.  I plan to use GEE to account for my phylogeny, rather 
than conventional contrast values, because I have a relatively small 
sample size and a variety of continuous and multilevel discrete 
factors.  The statistical problem is analogous to data which is 
spatially autocorrelated.  Thoughts?

Thanks,
BriAnne





~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
BriAnne Addison
Ecology, Evolution and Systematics
Biology Department
University of Missouri - St Louis

brianne.addison at umsl.edu

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