st: How to test the significance of a ratio of two correlated odds ratios in Stata

["Tiago V. Pereira" <tiago.pereira@mbe.bio.br>]

Dear statalisters,

I would like to obtain the ratio of two odds ratios from a simple logistic
regression model. The model I am working on looks like:

*/ ---------- start ---------------------

clear
set obs 1000
*/ generates a 1/0 disease status, 1 = disease,0=healthy
gene status = round(runiform())
*/generates a categorical covariate 0,1,2
gene covariate = round(runiform()*2)
logit status covariate
xi:logit status i.covariate

*/ ----------end ---------------------

Specifically, what I looking for is the ratio of  OR2 to OR1 (i.e. test if
this ratio is statistically significant from 1), where:

OR2 = odds ratio for covariate ==2 vs covariate ==0
OR1 = odds ratio for covariate ==1 vs covariate ==0

Maarten has already provided me some extremely useful insights in 2007 on
how to solve this problem in Stata

http://www.stata.com/statalist/archive/2007-02/msg00822.html

but I am somehow confused now when fitting that simple model.

If you could provide any further tips, I will be again very grateful.

All the best,

Tiago


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