From: hpdutra <hpdutra_at_yahoo.com>

Date: Sun, 06 Jul 2008 11:07:01 -0700 (PDT)

Date: Sun, 06 Jul 2008 11:07:01 -0700 (PDT)

First I would like to say thank you for taking the time to read it.Here is my problem.

> model<-lmer(track~veget*fruit*time*(time|plate)*(1|block),family=binomial)

*> summary(model)
*

Generalized linear mixed model fit by the Laplace approximation
Formula: track ~ veget * fruit * time * (time | plate) * (1 | block)

AIC BIC logLik deviance

933.9 994.5 -454.9 909.9

Random effects:

Groups Name Variance Std.Dev. Corr plate (Intercept) 0.226747 0.47618 time 0.054497 0.23345 -1.000 block (Intercept) 0.615283 0.78440Number of obs: 1152, groups: plate, 192; block, 3

Fixed effects:

Estimate Std. Error z value Pr(>|z|) (Intercept) -1.68645 0.58718 -2.8721 0.00408 ** vegetremoved -1.39291 0.57742 -2.4123 0.01585 * fruitremoved -0.54486 0.53765 -1.0134 0.31086 time -0.02091 0.10118 -0.2067 0.83626 vegetremoved:fruitremoved 0.75130 0.86342 0.8701 0.38422 vegetremoved:time 0.38229 0.14695 2.6014 0.00928 ** fruitremoved:time 0.17012 0.14227 1.1958 0.23178 vegetremoved:fruitremoved:time -0.47526 0.22134 -2.14730.03177 *

--- OK, the method that I am using is Laplace and someone has pointed out that this is more accurate than PQL. I am still confused about the structure of the model though. I want time to be a fixed effects but I also want it to be repeated measures giving that I sample the same plates multiple times, this way I have time appearing twice in my model, is this correct? The variable plate is the identity of each of the 192 plates. But I am not sure if this is the correct approach, because this approach establishes that the plates are the replication unit and I wonder if I should use the plot as the replication unit? But if I do that then I change the approach from a binary data (the plate had a paw print or not) to continuos variable in which I would count the number of plates in plot that had paw print. I am not sure which is the best approach? Am I in the right track? Thanks Humberto PS: I would like to say that posted kind of the similar post before but addressing different questions. I deleted the previous post to avoid confusion -- View this message in context: http://www.nabble.com/What-is-my-replication-unit--Lmer-for-binary-longitudinal-data-with-blocks-and-two-treaments.-tp18304494p18304494.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help_at_r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.Received on Sun 06 Jul 2008 - 18:14:25 GMT

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