Ciao,
yes I perfectly agree with you, I was just trying to summarise possible Rob points :)
Francesco
On Tuesday 02 July 2013 09:56:21 Diego Martinez Santos wrote: |Ciao | |I'm not sure they speak about "global tension", I mean, what they say |is different from making a chi2 with 24 DoF. From the abstract: |"Considering the 24 measurements as independent, the probability to observe |such a discrepancy in one of them is 0:5%." | |i.e, I guess they just mean that in 0.5% of experiments made of 24 |indepenendent measurements you have at least a discrepancy of 3.7 s or more |(and seem consistent with the toy I made). | |Cheers; | |Diego | |________________________________________ |Dende: Francesco Dettori [fdettori@nikhef.nl] |Enviado: martes, 02 de xullo de 2013 11:46 |Ata: bfys-physics@nikhef.nl |Cc: Rob Lambert; Diego Martinez Santos; Marcel Merk |Asunto: Re: [Bfys-physics] B->K*mumu paper | |Ciao Rob, | |I don't understand completely what is your point: |- that they should not claim any discrepancy because globally the agreement |is fine |- or that the final claim of 2.8 sigma global tension is wrong. | |cheers, |Francesco | |On Tuesday 02 July 2013 09:33:44 Rob Lambert wrote: ||Hi Again, || ||Another way to think about it is to fit a Gaussian to the 24 data points, ||and analyse whether one of them is an outlier or not. This is analytic ||given a Gaussian distribution with one outlier and reduces to the Chebychev ||inequality (or at least, I thought it did). || ||Thanks, || ||Rob || ||------------------------------------------ ||Robert Lambert ||FOM-VU-NIKHEF-Bfys LHCb ||Email: rob.lambert@cern.ch ||------------------------------------------ ||Nikhef N251 ||Tel: +31 20 592 2131 ||Fax: +31 20 592 5155 ||------------------------------------------ ||CERN, 13-1-018 ||Tel: +41 22 767 4024 ||Fax: +41 22 766 8109 ||------------------------------------------ ||________________________________ ||From: bfys-physics-bounces@nikhef.nl [bfys-physics-bounces@nikhef.nl] on ||behalf of Rob Lambert [Rob.Lambert@cern.ch] Sent: 02 July 2013 11:30 ||To: Diego Martinez Santos; Marcel Merk ||Cc: bfys-physics@nikhef.nl ||Subject: Re: [Bfys-physics] B->K*mumu paper || ||(24*0.0001*2) || || ^ missed a zero .... || ||Rob || ||------------------------------------------ ||Robert Lambert ||FOM-VU-NIKHEF-Bfys LHCb ||Email: rob.lambert@cern.ch ||------------------------------------------ ||Nikhef N251 ||Tel: +31 20 592 2131 ||Fax: +31 20 592 5155 ||------------------------------------------ ||CERN, 13-1-018 ||Tel: +41 22 767 4024 ||Fax: +41 22 766 8109 ||------------------------------------------ ||________________________________ ||From: Rob Lambert ||Sent: 02 July 2013 11:29 ||To: Diego Martinez Santos; Marcel Merk ||Cc: bfys-physics@nikhef.nl ||Subject: RE: [Bfys-physics] B->K*mumu paper || ||Hi Diego, || ||Well, I'm 100% sure that's right because it's just 24*0.001*2, which is the ||integrated probability for a two-sided Gaussian test, but the question isn't ||"what's the probability of that happening" which is actually "1", because it ||did actually happen, but "how many such deviations would you need to see ||before you can invalidate the null hypothesis of no deviation", and this ||number is given by Chebychev's equality... well, I thought it was, anyway. || ||Thanks, || ||Rob || ||------------------------------------------ ||Robert Lambert ||FOM-VU-NIKHEF-Bfys LHCb ||Email: rob.lambert@cern.ch ||------------------------------------------ ||Nikhef N251 ||Tel: +31 20 592 2131 ||Fax: +31 20 592 5155 ||------------------------------------------ ||CERN, 13-1-018 ||Tel: +41 22 767 4024 ||Fax: +41 22 766 8109 ||------------------------------------------ ||________________________________ ||From: Diego Martinez Santos ||Sent: 02 July 2013 11:17 ||To: Rob Lambert; Marcel Merk ||Cc: bfys-physics@nikhef.nl ||Subject: RE: [Bfys-physics] B->K*mumu paper || || ||(PS: 0.566 \pm 0.033. forgot the % of course) || ||________________________________ ||Dende: Diego Martinez Santos ||Enviado: martes, 02 de xullo de 2013 11:16 ||Ata: Rob Lambert; Marcel Merk ||Cc: bfys-physics@nikhef.nl ||Asunto: RE: [Bfys-physics] B->K*mumu paper || || ||Hi || || || ||I;ve just made quick toyMC, I get that the probability(maxSigma) > 3.7 for ||experiments consisting || ||of 24 measurements is 0.566 \pm 0.033. || || || || || ||Voila the code (needs SetupUrania): || || || ||from scipy import random as rnd ||from Urania import * ||AccessPackage("Bs2MuMu") || ||from RTuple import * || ||def do_set_of_experiments(N): || l = [] || || for i in range(N): || l.append(abs(rnd.normal())) || || l.sort() || l.reverse() || return l[0] || ||def do_test(N, Nexp = 50000): || tup = RTuple("File_test",["maxSigma/F"]) || || for i in range(Nexp): || tup.fillItem("maxSigma",do_set_of_experiments(24)) || tup.fill() || || tup.close() || ||Then you just call do_test(24) and analyse the produced Ntuple. || || || || || || || ||Cheers; || || || ||Diego || || || || || || || || || ||________________________________ ||Dende: bfys-physics-bounces@nikhef.nl [bfys-physics-bounces@nikhef.nl] en ||nome de Rob Lambert [Rob.Lambert@cern.ch] Enviado: martes, 02 de xullo de ||2013 10:53 ||Ata: Marcel Merk ||Cc: bfys-physics@nikhef.nl ||Asunto: Re: [Bfys-physics] B->K*mumu paper || ||Yes. Chebychev's inequality gives an estimate for how often a deviation this ||large this should happen, and it seems to be perfectly within the realms of ||probability, in fact it seems to be expected, and even two such deviations ||would not be strange. || ||Gerhard might want to correct me here, though... || ||Cheers, || ||Rob || ||------------------------------------------ ||Robert Lambert ||FOM-VU-NIKHEF-Bfys LHCb ||Email: rob.lambert@cern.ch ||------------------------------------------ ||Nikhef N251 ||Tel: +31 20 592 2131 ||Fax: +31 20 592 5155 ||------------------------------------------ ||CERN, 13-1-018 ||Tel: +41 22 767 4024 ||Fax: +41 22 766 8109 ||------------------------------------------ ||________________________________ ||From: Marcel Merk [marcel.merk@nikhef.nl] ||Sent: 02 July 2013 10:51 ||To: Rob Lambert ||Cc: bfys-physics@nikhef.nl ||Subject: Re: [Bfys-physics] B->K*mumu paper || ||Hi Rob, ||Let me just clarify: you question the claim of 0.5%, is that correct? ||just to make sure I understand which point you comment on. ||cheers, ||- Marcel || || ||On 2 July 2013 10:06, Rob Lambert ||<Rob.Lambert@cern.chmailto:Rob.Lambert@cern.ch> wrote: Erm, just some ||statistical queries.. what about chebychev's inequality: || ||http://en.wikipedia.org/wiki/Chebyshev%27s_inequality || ||"No more than 1/k^{2} of the distribution's values can be more than k ||standard deviations away from the mean" || ||In this case it is 1/(3.7*3.7) which is 7%, and 24*7% is 1.75, so no more ||than 1.75 of the observables should be this far away. One deviation this ||large is perfectly expected from Chebychev's inequality. || ||Thanks, || ||Rob || ||------------------------------------------ ||Robert Lambert ||FOM-VU-NIKHEF-Bfys LHCb ||Email: rob.lambert@cern.chmailto:rob.lambert@cern.ch ||------------------------------------------ ||Nikhef N251 ||Tel: +31 20 592 2131tel:%2B31%2020%20592%202131 ||Fax: +31 20 592 5155tel:%2B31%2020%20592%205155 ||------------------------------------------ ||CERN, 13-1-018 ||Tel: +41 22 767 4024tel:%2B41%2022%20767%204024 ||Fax: +41 22 766 8109tel:%2B41%2022%20766%208109 ||------------------------------------------ ||________________________________ ||From: bfys-physics-bounces@nikhef.nlmailto:bfys-physics-bounces@nikhef.nl ||[bfys-physics-bounces@nikhef.nlmailto:bfys-physics-bounces@nikhef.nl] on ||behalf of Marcel Merk [marcel.merk@nikhef.nlmailto:marcel.merk@nikhef.nl] ||Sent: 01 July 2013 18:01 ||To: bfys-physics@nikhef.nlmailto:bfys-physics@nikhef.nl ||Subject: [Bfys-physics] B->K*mumu paper || ||Dear bfys-physics friend, ||This is to let you know that I collect comments to the paper below. ||To stimulate you to read it: we claim that the probability that the ||measurement is consistent with the Standard Model is only 0.5%. A local ||discrepancy of 3.7 sigma is observed. || || LHCb PAPER-2013-037: || "Measurement of form factor independent observables || || in the decay $B^0\to K^{*0}\mu^+\mu^-$" || || Link : https://cds.cern.ch/record/1557918 || Deadline : 09-Jul-2013 || ||best regards, ||- Marcel || ||_______________________________________________ ||Bfys-physics mailing list ||Bfys-physics@nikhef.nlmailto:Bfys-physics@nikhef.nl ||https://mailman.nikhef.nl/mailman/listinfo/bfys-physics | |--- | Francesco Dettori | Nikhef - VU | | +31 20 592 2230 (Nikhef) | +41 22 76 76284 (CERN)
--- Francesco Dettori Nikhef - VU
+31 20 592 2230 (Nikhef) +41 22 76 76284 (CERN)