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st: RE: Generating skewed distributions on closed intervals


From   "Maarten Buis" <M.Buis@fsw.vu.nl>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Generating skewed distributions on closed intervals
Date   Thu, 29 Sep 2005 09:35:08 +0200

you can have a look at the beta distribution
a normal distribution will never stay within an interval (except [minus infinity, plus infinity])


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu]On Behalf Of Reza C Daniels
Sent: donderdag 29 september 2005 9:25
To: statalist@hsphsun2.harvard.edu
Subject: st: Generating skewed distributions on closed intervals

Dear Statalisters

I have a categorical variable for agegroup in 10 year bands (e.g. 20-30
years old). I would like to convert the categorical age variable to a
continuous variable by imposing various distributions on the range of
each interval. I then want to conduct sensitivity analysis to my
distributional assumptions.

For example: let a = the lower limit and b = upper limit for each age
group (e.g. a= 20 years old, b= 30 years old). Keeping the [20,30]
example, the four distributions I want to examine are:

1) Uniformly distributed over [20,30].
2) Normally distributed on the closed interval [20,30], with mode at 25.
3) Positively skewed on the closed interval [20,30], with mode at 22.5.
4) Negatively skewed on the closed interval [20,30], with mode at 27.5.

I have tried various commands (including -drawnorm-), but am unable to
control my variance to ensure the tails are bounded by [20,30] in the
example above (generically, the interval [a,b]).

Any suggestions on the code for all four distributions above would be
very much appreciated.

With thanks,
Reza
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