[R-sig-ME] Replicating type III anova tests for glmer/GLMM
Emmanuel Curis
emmanuel.curis at parisdescartes.fr
Tue Feb 23 16:32:23 CET 2016
On Tue, Feb 23, 2016 at 01:06:18PM +0100, Francesco Romano wrote:
« On the other hand, I don't understand how Cai et al. (2012) p.842,
« "combined analysis experiments 1 and 2", reported the main effect
« of a factor with 4 levels via a single estimate, SE, z, p coefficient.
« How did they obtain this and is this the right way?
It's just a guess, but any sum-of-square can be seen as a particular
contrast, that is a particular combination of the coefficients in the
model (or of the different means, expressed another way) that is
tested against 0. So I guess this single estimate is the value of the
contrast associated to the corresponding sum-of-squares, and SE/z/p
are derived similarly.
You can play with multcomp::glht to test this, but knowing which
contrast is tested by which sum of square in a specific desing may be
tricky: it depends on the coding, on the (un)balance...
Kowing if this is the « right » way is I think the same debate that
knowing which kind of sum-of-square should be used and the question is
very application dependent. Just, if you don't know what this single
estimate estimates really, interpretation is at best difficult...
--
Emmanuel CURIS
emmanuel.curis at parisdescartes.fr
Page WWW: http://emmanuel.curis.online.fr/index.html
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