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


From   Doug Hemken <dehemken@wisc.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: higher occurrence of disease X in rare disease Y
Date   Thu, 05 Dec 2013 08:42:39 -0600

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/


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