st: Recreating Confidence Intervals after Poisson Regression

[Garret Christensen <garretchristensen@yahoo.com>]

I'm interested in working with (read: using as scalars) the confidence intervals created by a Poisson regression. 


If I were doing a linear regression, I'd just do what they say here 
http://www.maartenbuis.nl/publications/p-value.pdf, which is: 

reg outcome treatment, robust
local l95=_b[treatment] -
 invttail(e(df_r),0.025)*_se[treatment] 
local u95=_b[treatment] + invttail(e(df_r),0.025)*_se[treatment] 

But a Poisson regression like the following:
poisson outcome treatment, robust

doesn't have the residual degrees of freedom (e(df_r)), and even if it did, I 
don't think that's how Stata is creating the confidence intervals. There must be some other simple (complicated?) formula I can use to recreate 
CI's, given the stored values after a Poisson regression. Any 
suggestions?

thanks,
Garret Christensen

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