# Re: st: Standard error of a sum

 From "Clive Nicholas" <[email protected]> To [email protected] Subject Re: st: Standard error of a sum Date Tue, 13 Jun 2006 20:53:22 +0100 (BST)

```Meloria Meschi wrote:

> I have a silly problem that's driving me nuts.  I have estimated two
> production function, with AR(1) correction.  I got 7 point forecasts each
> and their standard errors (call each forecast series x1 and x2).  I have
> computed the confidence intervals for each of these forecasts.
>
> Then I have added the two forecasts into one series y=x1 + x2 and produced
> s.e. and confidence intervals for this series as well.  What I need now is
> a confidence interval for the sum of y (ie total production from the two
> sites).  How do I compute the standard error for this total? And does it
> actually make sense to do so?

What does

. summarize y, display

tell you? I'm assuming these functions are continuous, valid measurements
which have no bounds. If so, calculating standard errors should pose no
difficulties. But only _you_ can answer that question!

You're politely reminded not to send attachments to the list.

CLIVE NICHOLAS        |t: 0(044)7903 397793
Politics              |e: [email protected]
Newcastle University  |http://www.ncl.ac.uk/geps

Whereever you go and whatever you do, just remember this. No matter how
many like you, admire you, love you or adore you, the number of people
turning up to your funeral will be largely determined by local weather
conditions.

*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/
```