R help - Nov 2008 - sample size estimation for count (poisson?) data?

Is there a function in R that will allow me to estimate the sample  
size required from count data (poisson data?), given the known  
variance and desired margin of error and confidence interval?

My specific data set will be based on a survey of hikers that will be  
asked about the number of animals of species 'x' they observed during  
a given period. I need to know the number of hikers to interview. ie,  
I would like to calculate the mean number of species 'x' +/- margin of  
error with 95% confidence.

This is a simple exercise for normally distributed continuous data,  
but I'm running into roadblocks for count data.

Sincerely,
Shawn Morrison
	[[alternative HTML version deleted]]

The first hit for search on "sample size" and "poisson" on
Baron's
search engine web interface appears on target:

http://search.r-project.org/cgi-bin/namazu.cgi?query=%22sample+size%22+poisson&max=100&result=normal&sort=score&idxname=functions&idxname=Rhelp02a

Getting the same result from your console window requires a couple of  
extra back-slashes:

 > RSiteSearch(""sample size" poisson")
Error: syntax error
 > RSiteSearch("\"sample size\" poisson")
A search query has been submitted to http://search.r-project.org
The results page should open in your browser shortly.

-- 
David Winsemius
Heritage Labs


On Nov 12, 2008, at 2:46 PM, Shawn Morrison wrote:
> Is there a function in R that will allow me to estimate the sample
> size required from count data (poisson data?), given the known
> variance and desired margin of error and confidence interval?
>
> My specific data set will be based on a survey of hikers that will be
> asked about the number of animals of species 'x' they observed
during
> a given period. I need to know the number of hikers to interview. ie,
> I would like to calculate the mean number of species 'x' +/- margin
of
> error with 95% confidence.
>
> This is a simple exercise for normally distributed continuous data,
> but I'm running into roadblocks for count data.
>
> Sincerely,
> Shawn Morrison
> 	[[alternative HTML version deleted]]
>
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