st: robust hypothesis test for totals

["Dimitriy V. Masterov" <dvmaster@gmail.com>]

I would like to estimate a multiplicative treatment effect for a total
(rather than a mean) with a confidence interval. The outcome is very
left-skewed, with lots of zeros and a kangaroo-like tail.
Alternatively, I would like to conduct a hypothesis that the effect is
1.

Here's an example of what I am thinking of:

sysuse auto
bs ratio = _b[Domestic]/_b[Foreign], reps(100): total price, over(foreign)

Is bootstrapping the best approach or is there something better? Can
this or some other procedure be generalized to more than two groups?
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