> If N goes to infinity, i.e. at high or very high data multiplicity Rmerge > approaches Rmeas (Rrim).
Sure. And there is nothing incorrect, because the formulas are identical. 0.8*sd(i)/I = 0.8/(I/sd(i)) But if you sum also over a shell of hs, that notation is incomplete losing the <> (or Mn). That is the confusion at least on my side. BR -----Original Message----- From: Manfred S. Weiss [mailto:manfred.we...@helmholtz-berlin.de] Sent: Thursday, April 17, 2014 8:46 AM To: b...@hofkristallamt.org Cc: Bernhard Rupp; CCP4BB@jiscmail.ac.uk Subject: Re: [ccp4bb] Rmerge, Rmeas, I/sigma, Mn(I/sd) That's not quite correct. If N goes to infinity, i.e. at high or very high data multiplicity Rmerge approaches Rmeas (Rrim). At this point it does not matter whether you write Rmerge or Rmeas equals 0.8 * sd(I) / I For low multiplicity Rrim (or Rmeas) = 0.8*sd(i)/I is the correct expression. Cheers, Manfred On 16.04.2014 22:16, Bernhard Rupp wrote: > The 2006 Weiss expression - I guess from the context- is for a single > reflection h measured N times (and then is identical to my 8-23) while (8-24) > is valid for the Rmerge (defined in 8-15) of averaging over a shell with h > reflections each measured N times , which also explains why the two related > expressions in aimless necessarily have to be different. > > Somehow crystallographers historically invented their own linear merging > statistics instead of 'standard' descriptive statistics like the standard > error of the mean...still an unresolved mess see the papers/threads on cc1/2, > cc* etc... > > Best, BR > > -----Original Message----- > From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of > Roberto Battistutta > Sent: Wednesday, April 16, 2014 5:09 PM > To: CCP4BB@JISCMAIL.AC.UK > Subject: [ccp4bb] Rmerge, Rmeas, I/sigma, Mn(I/sd) > > Hi, > in the Rupp book the following relation is reported (on pag 415): > Rmerge 0.8/<I/s(I)> > referring to a relation of "the linear merging R-value with the > signal-to-noise ratio". > > in a 2006 CCP4bb, Manfred Weiss reported: > Rrim (or Rmeas) = 0.8*sd(i)/I > > so, > > First question: is it Rmerge or Rmeas (Rrim) that we are dealing with? > > Second question: at the denominator (of the Rupp way to write), it is the > aimless Mn(I/sd) (usually indicated as the real signal-to-noise ratio) or the > aimless I/sigma (very different from Mn(I/sd) with high redundancy)? > > Thank you very much for the clarification. > > Best, > Roberto. > > Roberto Battistutta > Associate Professor > Department of Chemistry > University of Padua > via Marzolo 1, 35131 Padova - ITALY > tel. +39.049.827.5262 > fax. +39.049.827.5829 > roberto.battistu...@unipd.it > www.chimica.unipd.it/roberto.battistutta/ > VIMM (Venetian Institute of Molecular Medicine) via Orus 2, 35129 > Padova - ITALY tel. +39.049.7923.236 fax +39.049.7923.250 www.vimm.it -- Dr. Manfred. S. Weiss Helmholtz-Zentrum Berlin f r Materialien und Energie Macromolecular Crystallography (HZB-MX) Albert-Einstein-Str. 15 D-12489 Berlin GERMANY Fon: +49-30-806213149 Fax: +49-30-806214975 Web: http://www.helmholtz-berlin.de/bessy-mx Email: mswe...@helmholtz-berlin.de ________________________________ Helmholtz-Zentrum Berlin f r Materialien und Energie GmbH Mitglied der Hermann von Helmholtz-Gemeinschaft Deutscher Forschungszentren e.V. Aufsichtsrat: Vorsitzender Prof. Dr. Dr. h.c. mult. Joachim Treusch, stv. Vorsitzende Dr. Beatrix Vierkorn-Rudolph Gesch ftsf hrung: Prof. Dr. Anke Rita Kaysser-Pyzalla, Thomas Frederking Sitz Berlin, AG Charlottenburg, 89 HRB 5583 Postadresse: Hahn-Meitner-Platz 1 D-14109 Berlin http://www.helmholtz-berlin.de
