[Rivet] YODA development

[Ben Waugh]

On 30/10/09 11:47, Andy Buckley wrote:
> I'm not sure... I looked in the stats literature quite a lot to find a 
> definitive treatment of weighted stats combination (especially where 
> negative weights are concerned) and found nothing, hence the bullet 
> points are my invention. Perhaps it's sensitive to how the weights are 
> determined as to whether high weights are statistically equivalent to 
> many small weights, but I'm inclined to agree that my bullet points 
> aren't the whole story and that we need a more careful treatment. 
> Fortunately, the code in YODA that handles this for all histo types is 
> very localised! (in Dbn1D)
> 
> Any suggestions of alternative weighted combination recipes, which 
> consistently handle positive and negative weights? Or, better, has 
> anyone found any papers or books that address this issue?

I remember a useful preprint I used in my H1 days that gave some useful 
recipes and derivations, but of course I can't find it now. No luck 
finding anythin more authoritative either.

My recollection/understanding is that the "standard" recipe actually 
does work for negative weights: (1+-1) - (1+-1) = (0 += sqrt(2))...

Cheers,
Ben

-- 
Dr Ben Waugh                                   Tel. +44 (0)20 7679 7223
Dept of Physics and Astronomy                  Internal: 37223
University College London
London WC1E 6BT