# Re: st: Weighted daily mean

 From Neil Shephard To statalist@hsphsun2.harvard.edu Subject Re: st: Weighted daily mean Date Thu, 16 Oct 2008 12:15:07 +0100

```Beatrice Crozza wrote:
> Dear all,
>
> maybe again a simple question, but I tried to read the help and I
> didn't find a solution.
>
> I have calculated a daily mean for my variable trade, typing:
>
>
> now I want to calculate the total mean, so I typed:
>
>
> but I don't think that the result is correct.
>
>
Why don't you think the result is correct?

> Do you have any idea of how to calculate a mean, taking into account
> the daily mean?
>
I think you've got the wrong answer because you are treating each day as
equal, when in fact one day may have more observations than another.  In
these instances you want to apply a weight to the daily trademean that
you are including.  However its simpler to just work with the raw data
and take the overall mean for the period you are analysing, in which
case you just ignore the -, by(date)- option..

Neil

--
"We should make things as simple as possible, but not simpler" - Anon (not Albert Einstein)

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