Sample size when Population distribution is Poisson
- From: "Pat" <patrab@xxxxxxxxx>
- Date: 25 Sep 2006 10:54:27 -0700
Hi,
I was trying to estimate the correct sample size when the
population consists of count data (# of treatments per year) and am
somewhat confused. The population distribution should be Poisson in
this case : right ?
I was trying to use the formula for sample size :
sample size = (Z*SD/E)^2
where Z = critical value corresponding to desired confidence level
SD = standard deviation
E = margin of error.
I do not know the population Standard deviation but have a sample from
which it can be estimated. Now since the population follows a poisson
distribution, should I assume that the sample variance = sample mean
and use the following formula (for Standard deviation)
SD = sqrt(Sample Mean)
Can I use this estimation of SD in the previous formula to obtain the
correct sample size?
I would appreciate any help in this matter.
Thanks,
Pat
.
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