Fisher exact test

[May Au]

Hi, I use Stata 12. I'm looking for ways to do 400 different fisher exact tests efficiently. So instead of doing "tabi 12 2\37, exact" 400 times, is there a way i can incorporate the commands in a do file? I have 400 different 2x2 tables, and they're arranged into a big table with 400 rows and 4 columns; each column in a row represents a cell in the 2x2 table. Any help will be greatly appreciated!

[Joe Canner]

May,

Here's a quick-n-dirty way (assumes your 4 column variables are c1, c2, c3, and c4 and they are all non-missing):

forvalues x=1/`=_N' {
  tabi `=c1[`x']' `=c2[`x']' \  `=c3[`x']' `=c4[`x']' , exact
}

Regards,
Joe

[May Au]

Thanks, Joe. One more question. So how can I save the test statistics of the 400 tests into a table? Thanks again.

May

[Joe Canner]

The resulting p-values are in the scalars r(p_exact) and r(p1_exact). So, you could do the following, for example:

gen p=.
gen p1=.
forvalues x=1/`=_N' {  
  tabi `=c1[`x']' `=c2[`x']' \  `=c3[`x']' `=c4[`x']' , exact  
  replace p=`r(p_exact)' in `x'  
  replace p1=`r(p1_exact)' in `x'  
 }

[Nick Cox]

See also this FAQ for related technique http://www.stata.com/support/faqs/da...iate-commands/