[Rivet] Rivet "collaboration meeting"?

[Frank Siegert]

Hi again,

>> By the way... speaking about new features: I've written a simple
>> wrapper for the AIDA histograms to take into account correlated events
>> (e.g. NLO counter events), which I've been using in a private
>> analysis. Do you think it's still worth to put something like that
>> into SVN contrib?
>
> Absolutely!

I wanted to add this to SVN contrib now, but I noticed one issue with
our histograms (giving me a slight discrepancy in my tests) that I
wanted to understand.

We calculate the error on a given bin as something like
s^2 = sum(w^2)/n^2, cf.
https://rivet.hepforge.org/trac/browser/branches/2012-06-aidarivet/include/LWH/Histogram1D.h#L294
https://yoda.hepforge.org/trac/browser/trunk/include/YODA/HistoBin1D.h#L109

Why is this not using the normal variance a la
s^2 = 1/(n-1) <(w-<w>)^2>
   = 1/(n-1) (<w^2> - <w>^2)
   = 1/(n-1) (sum(w^2)/n - sum(w)^2/n^2)
?

Cheers,
Frank