Hi all,

I have been frustrated by what seems to me like inconsistent terminology
associated with binomial regression.  There are two questions I'd love to
have answered, below.

For context, I have been using glm with binomial error, logit link.  The
response variable is "successes and failures" -- the successes are the days
on which a species is observed in a year, and the failures are days in which
it is not observed.  So the code
is  glm(cbind(DaysPresent,DaysAbsent)~years,binomial).  I'm interested in
the coefficient associated with years as a way to express the decline in the
number of days a species is observed over time.

Question:

(1) This probably seems silly, but is "logistic regression" the same as a
glm with binomial error?  This is where I have found some frustrating
inconsistency in the ecological literature.

(2) What's the most straightforward way to interpret the coefficients from a
predictor variable in a model like the one specified above?  For example, a
species in decline (observed in fewer days over time) will have a years
coefficient of -0.14.  I'd like a verbal interpretation of that number.
 Rather than give you my understanding, I'll just ask and hope someone can
help me out!

thanks!
Matt




-- 
Matthew L Forister
Assistant Professor
Dept. of Biology / MS 314
1664 N. Virginia St.
University of Nevada, Reno
Reno, Nevada 89557
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