Help with logistic model with random effects in R

Ben Bolker · 2011-01-19T22:05:02Z

LAURA WEIR student.gla.ac.uk> writes: > > Hello everyone, > > I'm quite new to R and am trying to run a logistic model > to look at how various measures of boldness in > individual animals influences probability of capture, > however I also want to include random effects and > I'm not sure how to construct a model that incorporates both > of these things. > > Data was collected from 6 different groups of 6 individuals > with 10 replicates for each group. Whether an > indiv

Ben Bolker

Wed, Jan 19, 2011 2:05 PM

LAURA WEIR <0611792W <at> student.gla.ac.uk> writes:

I'm a little confused about your experimental design.  You say you
have 10 replicates per group, but I only see 36 observations in your
data set -- from your description I would have expected 360?

If you had 10 replicates per group I would say should do something like

glmer(Catchability~[fixed effect predictors]+(1|Group/Individual),
   family=binomial,data=data)

  A couple of other points:
* it's considered bad practice to name your data set 'data' (which is
also the name of a built-in R function).  Usually it's OK, but occasionally
it could cause problems.
* A rule of thumb is that you should not try to fit a model with
more than k=N/10 parameters, where for binary data 'N' is the minimum
of (number of successes, number of failures).
* 6 groups is at the lower edge of feasibility for fitting a random
effect -- you may find that glmer estimates the group-level variance
as zero. (Don't panic.)

  I would suggest that you send follow-ups to r-sig-mixed-models at r-project.org
and possibly take a look at <http://glmm.wikidot.com/faq>

  cheers
    Ben Bolker

Help with logistic model with random effects in R

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