Dear All,

I have two questions about reporting results from a binomial GLM (logit
link) that includes a categorical variable.  I understand how dummy coding
works.  My two questions are about interpretation and presentation:

1) The default in R seems to be to use the first level of a categorical
variable as the reference.  It makes more sense to me to use the grand mean
as the reference -- I found a webpage that describes this as "deviation
coding".  This seems so commonsensical, that I'm surprised that I don't see
more people using it instead of the default comparison to the first level.
 Am I missing something here? is this deviation coding a reasonable way to
go?  This is the website where I found that:
http://www.ats.ucla.edu/stat/r/library/contrast_coding.htm

2) Whether I use the default in R or switch to deviation coding, I will get
multiple coefficients associated with the different levels of my predictor
variable.  What is the convention for reporting the information associated
with the "dummy coded" levels of a categorical variable?  I had assumed
that I would report details associated with each of the dummy coded levels,
but I can't seem to find an example where someone has done that...

thanks for your help,
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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