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From |
dr kardos laszlo <l_kardos@chello.hu> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: RE: RE: probability question |

Date |
Thu, 29 Oct 2009 11:41:38 +0100 |

hi all,

. di comb(116,4)*comb(4,3)/comb(120,7) .00048146 laszlo Richard Goldstein wrote:

thank you -- that's quite interesting and means I did not think things through sufficiently when I replied to Paul -- sorry about that Edgar Munoz wrote:I like this approach using tabi as a calculator for this. r(p_exact) is P(n11 >= 3), the p-value in the Fisher's exact test if we calculate P(n11 >= 4), we can obtain P(n11 = 3) by difference . tabi 4 0 \ 3 113, exact | col row | 1 2 | Total -----------+----------------------+----------1 | 4 0 | 42 | 3 113 | 116-----------+----------------------+----------Total | 7 113 | 120Fisher's exact = 0.000 1-sided Fisher's exact = 0.000 . return list scalars: r(p1_exact) = 4.26072210718e-06 r(p_exact) = 4.26072210718e-06 r(c) = 2 r(r) = 2 r(N) = 120 | p3exact p3plus p4plus | |--------------------------------| 1. | .0004815 .0004857 4.26e-06 | -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Visintainer PhD, Paul Sent: Wednesday, October 28, 2009 7:49 AM To: 'statalist@hsphsun2.harvard.edu' Subject: st: RE: probability question I'm probably thinking of this too simplistically, but wouldn't this just be a Fisher's exact test? . tabi 3 1 \ 4 112, exact /* where col = rain and row = hat */ | col row | 1 2 | Total -----------+----------------------+----------1 | 3 1 | 42 | 4 112 | 116-----------+----------------------+----------Total | 7 113 | 120Fisher's exact = 0.000 1-sided Fisher's exact = 0.000 . return list scalars: r(p1_exact) = .0004857223202188 r(p_exact) = .0004857223202188 r(c) = 2 r(r) = 2 r(N) = 120 ___________________________________ Paul F. Visintainer, PhD -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Richard Goldstein Sent: Wednesday, October 28, 2009 8:38 AM To: statalist Subject: st: probability question it's been a long time since I thought about questions like this, but, as a lead-in to a study, a client has asked the following question which he thinks he understands and says is related to where he wants to go: during a consecutive period of 120 days, if it rains on 7 days and my client wears a hat on 4 days (these are independent of any knowledge of the weather), what is the probability that it will rain on 3 of the days on which he is wearing a hat? my client swears that this is not a homework problem for him or his wife or one of their kids! Rich* * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: probability question***From:*Richard Goldstein <richgold@ix.netcom.com>

**st: RE: probability question***From:*"Visintainer PhD, Paul" <Paul.Visintainer@baystatehealth.org>

**st: RE: RE: probability question***From:*"Edgar Munoz" <munozedg@hotmail.com>

**Re: st: RE: RE: probability question***From:*Richard Goldstein <richgold@ix.netcom.com>

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