RE: TGraphAssymm BAYESDivide

Dear H.

That depends on whether you're willing to condition your statistics (i.e. the vertical error bars) on the total number of events observed in each bin (the sum of the inner and outer counts).

If you are, your problem reduces to the Binomial, and TGraphAsymmError's "Divide" method (BayesDivide just calls it, nothing Bayesian there) is one of many that handle that. Personally, I'd never use their "shortest interval" approach, but obviously, opinions differ on that :-) TEfficiency is a newer, cleaner, and more flexible tool that handles Binomial errors. You may want to look at it.

BTW: once it's a Binomial problem, just sum the inner and outer counts to get the total.

If you're not willing to apply this conditioning, you'll need to program the errors in yourself. Also may want to think about which errors: Gaussian approximation? Frequentist intervals (with "exact" or on-average) coverage)? etc. Depends on what you want to use them for...

 cheers,
 Amnon Harel,
 University of Rochester

-----Original Message-----
From: owner-roottalk_at_root.cern.ch on behalf of HSing Sent: Mon 31-Jan-11 6:20 PM
To: roottalk (Mailing list discussing all aspects of the ROOT system.) Subject: [ROOT] TGraphAssymm BAYESDivide

Hello,

I am wondering if I can calculate Assymetric error on my datapoints usng BayesDivide fcn. The only problem is that I am doing ratio of 2 histograms , Number of evts in inner rapidity region/number of events in outer rapidity region.

But BayesDivide says that TAssymError::BayesDivide(h1,h2)

h1 should be subset of h2. But in my case, my h1 is not a subset of h2.

Could anybody suggest?

H. Received on Mon Jan 31 2011 - 17:42:49 CET