Re: st: how to find the integral for a portion of a normal distribution.

[Jeph Herrin <junk@spandrel.net>]

The total area under any normal curve is always 1, so you just need
to count obs:

 drawnorm x , means(2.02) sds(1.75) n(100000) clear
 gen byte lessthan1=x<=1
 sum lessthan1

The mean value of -lessthan1- is the area under the curve
to the left of 1.

hth,
Jeph


Buzz Burhans wrote:
> My weak math skills are showing up here - 
>
> For demonstration purposes, I have generated a set of 100,000 observations
> with a normal distribution, mean 2.02, SD 1.74 and visualized this data and
> the portion of observations above 1  with a histogram
>
> drawnorm x , means(2.02) sds(1.75) n(100,000) clear
> hist, xline(1)
>
> I also computed the proportion of the observations <=1 from the Z score.
>
> What I don't know how to do in Stata is find the integral for the
> proportions of the distribution above and below 1.  
>
> How can I determine those two integrals in Stata?
>
> Thanks
>
>
>
> Buzz Burhans, Ph.D. 
>
> Dairy-Tech Group
> So. Albany, VT / Twin Falls ID
>
> Phone: 802-755-6842
> Cell: 208-320-0829
> Fax VT: 802-755-6842
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>
> Email: buzzb3@earthlink.net
>
>
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