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> -------------- next part -------------- An embedded and charset-unspecified text was scrubbed... Name: not available URL: <https://stat.ethz.ch/pipermail/r-sig-mixed-models/attachments/20141107/30b4525e/attachment.pl>
MCMCglmm Heterogenous Residual Variance in a Categorial Model
2 messages · FERNANDEZ Ana maria, Jarrod Hadfield
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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