-----Original Message-----
From: R-sig-mixed-models [mailto:r-sig-mixed-models-bounces at r-
project.org] On Behalf Of Emmanuel Curis
Sent: February 23, 2016 10:32 AM
To: Francesco Romano <francescobryanromano at gmail.com>
Cc: r-sig-mixed-models at r-project.org
Subject: Re: [R-sig-ME] Replicating type III anova tests for glmer/GLMM
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