Hi, I am not sure about the 1.2-1.3 limit, but 0.8 probably comes from sqrt(2/pi), which is the ratio of the mean of a half-normal and its sigma when the mean parameter is 0.
Best wishes, Gergely From: CCP4 bulletin board <CCP4BB@JISCMAIL.AC.UK> On Behalf Of David Waterman Sent: 18 December, 2020 12:53 To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] Anomalous signal to noise details Hi folks The paper "Substructure solution with SHELXD<https://journals.iucr.org/d/issues/2002/10/02/gr2280/index.html>" (Schneider & Sheldrick, 2002) describes how data can be truncated at the resolution at which [ΔF to its estimated standard deviation as a function of the resolution] drops to below about 1.3 Is this referring to the quantity <|ΔF|>/<σ(ΔF)> calculated in resolution shells, or the quantity <|ΔF|/σ(ΔF)> ? This entry<https://strucbio.biologie.uni-konstanz.de/ccp4wiki/index.php?title=SHELX_C/D/E#Resolution_cutoff_.28SHEL.29> on the ccp4wiki gives a cutoff where the mean value of |ΔF|/σ(ΔF) falls below about 1.2 (a value of 0.8 would indicate pure noise) this version sounds to me like <|ΔF|/σ(ΔF)> which is the "better" metric, and what do people mean when they say DANO/SIGDANO? What is the justification for the 1.3 (or 1.2) value? Thanks! -- David ________________________________ To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
