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Message: 2
Date: Wed, 23 Oct 2013 15:48:42 +0100 (BST)
From: Stefan Ferger <stefan.ferger at yahoo.de>
To: "r-sig-mixed-models at r-project.org"
<r-sig-mixed-models at r-project.org>
Subject: [R-sig-ME] Zero-inflated binomial (ZIB) models in glmmADMB:
warnings and errors
Message-ID:
<1382539722.1360.YahooMailNeo at web171701.mail.ir2.yahoo.com>
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1) None of the models shown above produces any warnings or errors when I run them with glmer (and thus ignore the zero-inflation).
2) When I sum all pecks on plot level and leave out cluster completely, I get much less zeros (but also much less replicates). When again modeled in glmer without controlling for zero-inflation the results are qualitatively the same as in 1), but the overdispersion is becoming much stronger (ratio ~ 3.5). Correcting for this by incorporating an observation-level random effect, however, leads to strong underdispersion (ratio ~ 0.3) and differing results.
3) I nevertheless think that the model structure should be determined by the design and therefore I would like to go for the version that appreciates the clusters, which means that I have to deal with these zeros.
Does anybody know what I could do to fit these models in glmmADMBsuccessfully? Do I actually need to account for this zero-inflation, the consensus seems to be that one should do so if there are "over-proportionally" many zeros - but when is this threshold passed?
As fitting the models successfully in glmmADMB might be tricky, does anybody know how the model structure should look like in one of the other packages, i.e. MCMCglmm (I found the model specification very tricky here) or R-INLA?
Thank you for your help,
Stefan