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

 From Jeph Herrin To statalist@hsphsun2.harvard.edu Subject Re: st: how to find the integral for a portion of a normal distribution. Date Tue, 04 May 2010 12:15:29 -0400

```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
Fax ID: 208-735-1289

Email: buzzb3@earthlink.net

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```
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