<html style="direction: ltr;"> <head> <meta content="text/html; charset=utf-8" http-equiv="Content-Type"> <style type="text/css">body p { margin-bottom: 0cm; margin-top: 0pt; } </style> </head> <body style="direction: ltr;" bidimailui-charset-is-forced="true" text="#000000" bgcolor="#FFFFFF"> Hi Andy, oh sorry, our bad - we were only looking at the individual histograms. So what we were/are looking for is the number of 'attempts' which would differ from the number of 'events' by the count of events with zero weight (that also contribute to the calculation of the cross section). Obviously this would have to be communicated to Rivet from the generator for which there currently is no existing infrastructure, right? The motivation for this is to calculate the statistical MC error also using the second part "-(sum of weights)^2/N" where N is the number of attempts. You can find a copy of my master's thesis at <a href="http://www.itp.kit.edu/prep/diploma/PSFiles/ms-thesis-daniel-rauch.pdf"><a class="moz-txt-link-freetext" href="http://www.itp.kit.edu/prep/diploma/PSFiles/ms-thesis-daniel-rauch.pdf">http://www.itp.kit.edu/prep/diploma/PSFiles/ms-thesis-daniel-rauch.pdf</a></a> - the corresponding sections would be 4.2 & 4.3 for the equations for the combination of 1D histos and their MC errors, appendices B and C for the derivations and sec 5.4 for the implementation in the Herwig-Parallel toolset. <blockquote cite="mid:563B5BEF.8050302@cern.ch" type="cite">We're avoiding building any special interpretation of such variables into YODA (and especially yodamerge), so that it remains a generic data analysis package with capabilities useful for these studies, rather than a one-trick package specifically for MC analysis, so at a later point we plan to have a rivet-merge or similar script which will use the logic of yodamerge with added MC-specific use of this information. </blockquote> So I understand this is the reason for going with the sqrt( sum of ( weights^2 ) ) error definition - we will then most probably try to check if we can somehow develop similar patches for Rivet 2.4 to do the communication of the number of attempts from Herwig to Rivet. Many thanks, Daniel </body> </html>