st: Generating skewed distributions on closed intervals

[Reza C Daniels <rdaniels@commerce.uct.ac.za>]

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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