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Re: st: How to perform GLM with nested observations

From   Jeph Herrin <>
Subject   Re: st: How to perform GLM with nested observations
Date   Thu, 24 Jul 2008 15:46:31 -0400

Yes, I had typed -xtmepoisson- but then had this memory
of seeing 1m+ bats pour out of a cave in Thailand once
and thought maybe it would be ridiculous to assume that
bat counts were small integers. So I edited out the


Austin Nichols wrote:
With a depvar that is a count, I think you would prefer -xtmepoisson-
but the cluster option on -glm- or -poisson- is the place to start,
and with 500 sites there are no worries about insufficient clusters.

On Wed, Jul 23, 2008 at 12:33 PM, Jeph Herrin <> wrote:
See -xtmixed- wrote:
Dear List,

I have 500 sites, and each site contains twelve transects.

My dependent variable is the number of bats encountered along each

My independent variables have been measured at either transect or site
level and include:
habitat type (categorical) measured at transect level
distance to nearest water feature measured at transect level
proportion of woodland, measured at site level
density of water features, measured at site level

Is there a way I can include all 6000 observations and all independent
variables (both categorical and continuous and at both scales) in a
GLM-type analysis that, critically, allows for the lack of independence
between observations within the same site, caused by the nested sample

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