Re: st: calculating Fishers exact test and recording output for multiple two by two tables at once

[Phil Schumm <pschumm@uchicago.edu>]

On May 17, 2010, at 5:22 PM, Michael Walsh wrote:
> I would like to calculate a two-sided Fisher's exact test for many  
> studies in one data set and record the test value in a new column  
> (or file). The information from the two-by-two table occupies one  
> row for each study (col 1 = treatment events, col 2 = control  
> events, col 3 = treatment non-events, col 4 = control non-events).  
> Does anyone know of an existing Stata procedure that can accommodate  
> this?


Perhaps the easiest way to do this is with -statsby-.  For example,  
suppose that the two variables that comprise your two-by-two table(s)  
are called var1 and var2, and suppose that your studies are indexed by  
a variable called study.  In that case, the following will place the p- 
value and the cell frequencies into individual variables -- one  
observation per study:

    statsby p=r(p_exact) r1c1=mymat[1,1] r1c2=mymat[1,2] ///
                         r2c1=mymat[2,1] r2c2=mymat[2,2],  
by(study): ///
                         tab var1 var2, exact matcell(mymat)


-- Phil

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