[R-sig-ME] GLMM for proportions

[poulin]

Dear list,

I have a question regarding GLMM's for proportion fitted with lme4.

Such models are fitted using the binomial family. When I fit such 
models, I use, on the left side of the formula : cbind(success,failure).

Problem is when, for example, data are durations (duration of success 
and duration of failure) that are not integer numbers if speaking in 
seconds.
When fitting a GLM, one can use directly in the left part of the formula 
a variable that is the proportion of success. When trying to do this for 
a GLMM one will have the warning message : « In eval (family$initalize, 
rho): non-integer # successes in a binomial glm! »
To avoid this, biologists I work sometimes with, used ms instead of s 
for their duration times of success and failure but then the associated 
tests are too powerfull...
I am not able to tell if the displayed warning message is of concern or 
not.
So my question is : do you think it is better to use ms instead of s or 
directly the proportion?
Thanks in advance for any help that can be provided
Best regards

-- 
Nicolas Poulin
Ingénieur de Recherche
Centre de Statistique de Strasbourg (CeStatS)
http://www.math.unistra.fr/CeStatS/

Tél : 03 68 85 0189

IRMA, UMR 7501
Université de Strasbourg et CNRS
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67084 Strasbourg Cedex