Today's Topics:
1. Re: Post Hoc tests GLM (B.-Markus Clarin)
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Message: 1
Date: Mon, 14 Oct 2013 10:13:57 +0200
From: "B.-Markus Clarin" <b.markus.cla...@gmail.com>
To: Javier Atalah <javier.ata...@cawthron.org.nz>
Cc: "r-sig-ecology@r-project.org" <r-sig-ecology@r-project.org>
Subject: Re: [R-sig-eco] Post Hoc tests GLM
Message-ID:
<ca+r--qrk3kphvtyt+rjcrh3lttk6ehp9mwf8tgzbnquapxr...@mail.gmail.com>
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Dear Luis and Javier,
I am having a bit trouble understanding the model structure that was posted
in the original question:
glm(formula = Frec ~ Group+ Hour:Category, family = poisson)
I am an ecologist and I recall from all courses on statistical modelling,
that if I find an interaction term significant, I HAVE to retain the
related main effects as well, even if they have no significant effect by
themselves.
Never say 'you have to..' in statistics. See:
The Hierarchy Principle in Designed Industrial Experiments
Douglas C. Montgomery, Raymond H. Myers, Walter H. Carter, Jr. and G.
Geoffrey Vining
Qual. Reliab. Engng. Int. 2005; 21:197–201
Alain Zuur
--
Dr. Alain F. Zuur
First author of:
1. Analysing Ecological Data (2007)
2. Mixed effects models and extensions in ecology with R (2009)
3. A Beginner's Guide to R (2009)
4. Zero Inflated Models and GLMM with R (2012)
5. A Beginner's Guide to GAM (2012)
6. A Beginner's Guide to GLM and GLMM (2013)
Highland Statistics Ltd.
6 Laverock road
UK - AB41 6FN Newburgh
Tel: 0044 1358 788177
Email: highs...@highstat.com
URL: www.highstat.com
URL: www.brodgar.com
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