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st: simulating a lognormal distribution


From   Jeph Herrin <junk@spandrel.net>
To   statalist@hsphsun2.harvard.edu
Subject   st: simulating a lognormal distribution
Date   Tue, 12 Sep 2006 09:23:52 -0400

This is not, strictly speaking, a Stata problem, but I am hoping
to find a Stata solution.

I am trying to simulate a lognormal distribution, but have only
the median (which I'm willing to assume is the log mean) plus
the mean and sd of the non-log transformed data. Put another way,
I have median, mean and sd of Y, but log(Y) is normal, and I would
like to simulate Y.

I have found -rndlgn-, which will simulate a random log normal
distribution, but only if I have the mean and sd of log(Y). The
only idea I have is to generate a series of log normal distributions
X with mean = log(median(Y)) and a range of sds, until I end up with
one where exp(X) has the mean and sd of Y. But this seems overly
computing intensive for my purposes, as I will need to do this for
a large number of obs with a loop that runs many times.

Any other ideas? In particuar, am I missing an obvious way to get
the mean & sd of log(Y) from the mean and sd of Y?

thanks,
Jeph







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