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From |
Roger Newson <roger.newson@kcl.ac.uk> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: RE: probability models |

Date |
Mon, 07 Mar 2005 21:28:08 +0000 |

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 toFor 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. Nick n.j.cox@durham.ac.uk

mu_1/(mu_1+mu_2)

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.

Roger

--

Roger Newson

Lecturer in Medical Statistics

Department of Public Health Sciences

Division of Asthma, Allergy and Lung Biology

King's College London

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United Kingdom

Tel: 020 7848 6648 International +44 20 7848 6648

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or 020 7848 6605 International +44 20 7848 6605

Email: roger.newson@kcl.ac.uk

Website: http://phs.kcl.ac.uk/rogernewson/

Opinions expressed are those of the author, not the institution.

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**References**:**st: RE: probability models***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

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