Message-ID: <20141107203809.17832zk2s5vc7o4k@www.staffmail.ed.ac.uk>
Date: 2014-11-07T20:38:09Z
From: Jarrod Hadfield
Subject: MCMCglmm Heterogenous Residual Variance in a Categorial Model
In-Reply-To: <93CBC95C-6C8A-4234-B6BA-347BA18204BF@sms.ed.ac.uk>
Hi Maria,
You are right - for a categorical variable the units variance cannot
be estimated for either sex. You can safely use rcov=~units and set
the variance to one in the prior.
Cheers,
Jarrod
Quoting FERNANDEZ Ana maria <s1049258 at sms.ed.ac.uk> on Fri, 7 Nov 2014
11:18:04 +0000:
> Dear List,
>
> I was wondering what the recommendation is for structuring residual
> variances in the context of a categorial model when you have a sex
> interaction in the random term of the model (where animal is the
> pedigree structure).
>
> MCMCglmm course notes have a brief recommendation about sex
> interaction and allowing the sexes to have different residual
> variances: "3.4 Heterogenous Residual Variance To be started... In
> short - if you?ve fitted a sex by dam interaction I would always
> allow the sexes to have different residual variances. Use
> rcov=?idh(sex):units.?
>
> But the conflict that I am coming across is another recommendation
> about how the residual term should be- or needs to be- fixed in a
> categorical model.
>
> I have a case-control binary response variable and I want to look at
> the sex effect interaction.
>
> Let me know if you need more detail.
>
> Thanks!
> Maria
>
>
>
> Ana Maria Fern?ndez Pujals
> A.Fernandez-2 at sms.ed.ac.uk<mailto:A.Fernandez-2 at sms.ed.ac.uk>
>
>
>
>
>
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