st: How to compute with Stata probabilities by conditioning ?

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

Dear statalisters,

Imagine two standard normal variables, X and Y, with known correlation, rho.

P(X>t1|Y>t2) can be computed with

binormal(t1,t2,rho)

What if we were interest in computing

P(X>t1 and Y>t2) ?

Since X and Y are correlated, I am a bit confused.

I am using brute force (dumb way):

set obs 1000000000
matrix M = (1,rho \ rho, 1)
drawnorm x y, means(0 0) sds(1 1) corr(M)
count if x>t1&y>t2

P(X>t1 and Y>t2)  = r(N)/_N

Is there a smarter way of computing probabilities by conditioning (with
Stata)?

Thanks in advance.

Tiago


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