To Whome it May Concern,

I am currently analyzing the data from a toxicity test and I want to use a glmm with the lmer function in the lme4 package.

Experimental Design:
I exposed beakers of larval amphibians to different concentrations of metals contaminants at different temperatures. I'm primarily concerned with the effect of temperature on toxicity. I ran the test for 4 days and my response variable is proportional data (percent mortality) because I recorded the number dead per beaker. I therefore have percent mortality for each beaker at 0, 24, 48, 72, and 96 hours. I had 3 replicates of each treatment.

Statistics:
I want to incorporate time into the model and need to include the autocorrelation due to time (violation of the assumption of independence). I also have to account for the response variable being proportional with lots of 0's and 1's.

So far it looks like I have to do something like this:

m1<-lmer(PercentMortality~Time*Concentration*Temperature+(1|BeakerNumber),family=binomial)

I'm not sure if this accounts for the non-independence between times though. Do you have any suggestions as to the code I should use for this? Any help would be greatly appreciated as I've been having trouble finding examples of this type of analysis.

Cheers,

-
Tyler Hallman, M.S.
Ph.D. Student
The Robinson Lab
Department of Fisheries and Wildlife
Oregon State University Corvallis

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