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From |
Nick Cox <njcoxstata@gmail.com> |

To |
"statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |

Subject |
Re: st: higher occurrence of disease X in rare disease Y |

Date |
Thu, 5 Dec 2013 14:50:44 +0000 |

Doug's code is fine and suits the purpose perfectly. A footnote is to underline that Mata can be used to the same "smart calculator" end, e.g. . mata : X = (0..6)' : binomialp(6,X,1/36) 1 +---------------+ 1 | .8444875698 | 2 | .1447692977 | 3 | .0103406641 | 4 | .0003939301 | 5 | 8.44136e-06 | 6 | 9.64727e-08 | 7 | 4.59394e-10 | +---------------+ : binomialp(6,(0..6)',1/36) 1 +---------------+ 1 | .8444875698 | 2 | .1447692977 | 3 | .0103406641 | 4 | .0003939301 | 5 | 8.44136e-06 | 6 | 9.64727e-08 | 7 | 4.59394e-10 | +---------------+ Nick njcoxstata@gmail.com On 5 December 2013 14:42, Doug Hemken <dehemken@wisc.edu> wrote: > Here is a script that illustrates the probabilities using Stata, it is such a small problem that you can illustrate statistical power by trail-and-error: > > set obs 7 > gen X = _n - 1 > gen prob = binomialp(6,X,1/36) > gen prob10 = binomialp(10,X,1/36) > gen prob12 = binomialp(12,2*X,1/36) > > > On 12/05/13, Doug Hemken wrote: >> If your sample size is literally six cases, then your unconditional probability of seeing disease X is 0.145. If there is no relation between Y and X, it wouldn't be too unusual to see 1 case of X crop up in 6 cases of Y. This is from a binomial distribution. >> >> On 12/05/13, "tiong21@netzero.net" wrote: >> > The prevalence of disease (X) is 1 in 36 in the general population. In a sample population with a very rare disease (Y) of unknown etiology, the prevalence of disease X is 1 in 6 ( ie: 1 case of X was found in the sample population of 6 rare cases of disease Y. How do I show statistically that this higher occurrence of disease X in rare disease Y is not due to chance? And as a corollary suggest that disease X may be a contributory factor in the etiology of disease Y (an issue of causality). Furthermore, should a Poisson distribution be used to calculate the probabilities? A sample Stata script will be much appreciated. >> > >> > >> > Tiong The >> > tiong21@netzero.net >> > >> > * >> > * For searches and help try: >> > * http://www.stata.com/help.cgi?search >> > * http://www.stata.com/support/faqs/resources/statalist-faq/ >> > * http://www.ats.ucla.edu/stat/stata/ >> >> -- >> Doug Hemken >> 4226I Social Science Bldg. >> >> dehemken@wisc.edu >> 262-4327 >> * >> * For searches and help try: >> * http://www.stata.com/help.cgi?search >> * http://www.stata.com/support/faqs/resources/statalist-faq/ >> * http://www.ats.ucla.edu/stat/stata/ > > -- > Doug Hemken > 4226I Social Science Bldg. > > dehemken@wisc.edu > 262-4327 > > To make a consulting appointment send me an email, or use the on-line scheduler: > https://calendar.wisc.edu/scheduling-assistant/public/profiles/PlRxCykH.html > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/faqs/resources/statalist-faq/ > * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: higher occurrence of disease X in rare disease Y***From:*Doug Hemken <dehemken@wisc.edu>

**References**:**st: higher occurrence of disease X in rare disease Y***From:*"tiong21@netzero.net" <tiong21@netzero.net>

**Re: st: higher occurrence of disease X in rare disease Y***From:*Doug Hemken <dehemken@wisc.edu>

**Re: st: higher occurrence of disease X in rare disease Y***From:*Doug Hemken <dehemken@wisc.edu>

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