# Re: st: - uniform() - random variable not uniformlydistributed overinterval

 From "Hsuchi Ting" To Subject Re: st: - uniform() - random variable not uniformlydistributed overinterval Date Wed, 09 Mar 2005 20:37:33 -0500

```this is a follow-up question. I have been trying to generate random
integers instead of numbers distributed between 0 and 1. Could anyone
direct me to the command for doing this?

Sincerely,

ting

>>> DGarvey@scu.edu 03/09/05 8:19 PM >>>

Dear listers:

I am generating a random number with the goal of (randomly) assigning
children who report multiple races to a single race category for
purposes of analysis.  I'd like to evenly distribute children across
single race categories.  However, when I use uniform() to generate a
random number, I don't get an even split:

. gen r = uniform() if k_race == 801
(363374 missing values generated)

. su r

Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
r |      2309    .4995691    .2914078   .0007709   .9993796

. gen byte k_race2 = .
(365683 missing values generated)

. replace k_race2 = 100 if r <= 0.5

. replace k_race2 = 200 if r > 0.5 & r <= 1
k_race2 was byte now int

I am puzzled.  I would expect median = mean = 0.5 for a uniform number
defined over [0,1). This must be a simple, basic question, but neither
changing the - set seed -, changing the interval to [0,1], or changing
the observations selected seems to solve this problem.  A search of
on-line help, the list archives and the Stata FAQs didn't give me much
insight either.

Can you help me figure out what I'm doing wrong?

Thanks,

Deb Garvey

******************************
Deborah Garvey, Ph.D.
Department of Economics
Kenna Hall
Santa Clara University
Santa Clara, CA  95053
408/554-5580
408/554-2331 (FAX)
dgarvey@scu.edu
http://lsb.scu.edu/~dgarvey
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