I'm performing an analysis of behavioral variation among individual
tadpoles, using individual ID as a random effect and time as a continuous
fixed covariate in the lmer function in lmer4 package. I'm really
interested in making inferences about the random effect (i.e. the extent of
variation among individuals). I'd like to do two things that I can't seem
to find straightforward answers about and I'm hoping someone can help or
point me to a good resource.

1) The intraclass correlation coefficient is of particular interest to me,
as it describes the proportion of variation that occurs among individuals.
Ideally I'd like to report a confidence interval of the ICC but I can't
find any way to calculate one, other than a function in the psychometric
package that appears to only work when there are no covariates in the model
(random effect only).

2) A reviewer requested a power analysis of the ability to detect a
significant random effect. Any tips on how to approach that?

Thanks for any help,

Brad

-- 

Bradley Evan Carlson
PhD Candidate
Intercollege Graduate Degree Program in Ecology
The Pennsylvania State University
University Park, PA 16802

Email: carbrae@gmail.com
http://homes.bio.psu.edu/people/faculty/langkilde/index_files/carlson.htm
https://sites.google.com/site/bradleyecarlson/home

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