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Re: st: RE: probability models
At 12:35 07/03/2005, Nick Cox wrote (in reply to Blau Blau):
If you are really confident that the 2 Poisson variables you are comparing
really are Poisson, then you can use the fact that the conditional
distribution of the first one, given their sum, is binomial, with total
equal to their sum, and probability equal to
For the normal, you have -ttest- and -ttesti-.
A comparison of two Poisson means is
possible using -poisson-. I am not
aware of an immediate equivalent.
where mu_1 and mu_2 are the first and second Poisson population means.
Therefore, you can use -cii- to define a binomial confidence interval for
mu_1/(mu_1+mu_2), which should include 0.5 if mu_1 is equal to mu_2.
I hope this helps.
Lecturer in Medical Statistics
Department of Public Health Sciences
Division of Asthma, Allergy and Lung Biology
King's College London
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