[R-sig-ME] Multiple random and cross-classified factors specification and caveats in a generalized linear model (with MCMCglmm)
ned.dochtermann at gmail.com
Mon Mar 24 21:46:15 CET 2014
Since I tend to be verbose, the question eventually being asked below is
whether the model specification seems appropriate and, being unfamiliar
to this sort of categorical cross-classified model, whether there are
glaring problems I'm missing.
I'm trying to analyze a dataset of paired contest outputs with winners
and losers. I'm wanting to use a mixed model as opposed to an
alternative approach because I'm particularly interested in whether
there are different among-individual variances for a particular grouping
variable (handedness). Individuals show up as both focal individual and
opponent across multiple contests so there are a few ways in which
pseudoreplication enters the dataset.
The data basically looks like:
Focal.ID Opp.ID Contest.ID Handedness Won
Bob Jack 1 L
Jack Bob 1 R
Bob Sam 2 L W
Sam Bob 2 L L
Matt Sam 3 R W
Sam Matt 3 L L
John Steve 880 R
Steve John 880 L
We have 880 contests with 588 unique focal id's, with 58% of individuals
competing in at least one contest. Unfortunately some individuals had to
be excluded so both individuals from a contest aren't always included.
The fixed portion of the analysis includes only an intercept (based on a
published analysis someone else did and because of the specific
question). The random part of the model is then:
I'm then looking at the posterior distribution difference in latent
scale variances for lefties and righties. I don't actually care about
the variances of the other effects, they're just included because they
seemingly should be. The thought was that this sort of model structure
would at least partially encompass the data structure.
Does this structure seem reasonable?
I know detecting variance differences between groups is going to be
tough, but this is the data we could obtain.
Ned A. Dochtermann
Assistant Professor / Department of Biological Sciences
*NORTH DAKOTA **STATE UNIVERSITY*
p: 701.231.7353 / f: 701.231.7149 / www.ndsu.edu
ned.dochtermann at ndsu.edu
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