On Nov 25, 2009, at 7:04 AM, djpren wrote:
Thanks for the reply. Naturally I already searched the site and help
for the
answers to these questions. I think I've figured out how to run a
quasi-binomial model, but I cannot figure out how to test for
over-dispersion or how to apply a shapiro-wilk test.
This is not homework, neither do I have an instructor who is
proficient in
using R. This program was suggested to me by another researcher
after he
witnessed my frustration with the inflexibility of SPSS and other such
programs. I am on a very tight schedule and I don't have time to
become a
statistician and computer scientist, which is why I wrote 3 very quick
questions asking for commands that i had already tried to find myself.
"Quick questions" are somewhat deprecated here. Have you read the
Posting Guide? Its overall message is that the list readership expects
more detail rather than less. Perhaps with a better search method and
a pointer to the glm() function, which will do what was requested,
you might compose a more complete description of the data and the
problem, and offer code that shows what progress you are making.
Testing for over-dispersion is probably something I can eventually
get to
grips with, since I just have get variance for the real and modelled
data.
However, I cannot find a command to do shapiro-wilks on the site or
on these
forums.
I would have thought my original reply would have pointed the way to
more effective searching. The obvious search strategy using the
RSiteSearch function would seem to be:
> RSiteSearch("shapiro wilks")
A search query has been submitted to http://search.r-project.org
The results page should open in your browser shortly
A Browser window did open up and there were 8 hits, at least two of
which were to functions that would do what you appear to be determined
to do on a rather dubious basis.
Also, why do you say that most people here wouldn't recommend this
procedure?
Are you doing this because some reviewer asked you to do so or because
you are copying a path that someone else laid out for you? Testing for
normality in a binomial model seems rather puzzling on the face of it.
--
David.
David Winsemius wrote:
On Nov 24, 2009, at 3:41 PM, djpren wrote:
I am looking for the correct commands to do the following things:
1. I have a binomial logistic regression model and i want to test
for
overdispersion.
Under the teach a man to fish precept, ... try:
RSiteSearch("test over dispersion binomial models")
2. If I do indeed have overdispersion i need to then run a quasi-
binomial
model, but I'm not sure of the command.
?glm
# and follow the appropriate links
3. I can get the residuals of the model, but i need to then apply a
shapiro
wilk test to test them. Does anyone know the command for this?
RSiteSearch("shapiro-wilks") # not that people here recommend this
procedure
The overall flavor of these questions is "homework", so I'm
speculating that you may want to consult your instructors.
--
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
--
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______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
