From: "Whetton, Peter" To: 'Hans von Storch' , Congbin Fu , GIORGI FILIPPO , Bruce Hewitson , Mike Hulme , Jens Christensen , Linda Mearns , Richard Jones , "Whetton, Peter" Subject: RE: n-1 / n-2 Date: Thu, 14 Sep 2000 10:30:27 +1100 Dear all, It could be viewed that using n-1 for 9 models where we used n-1 for five models before is an implicit change in the stringency of our criterion. When we had five models, agreement (0/5, 1/5, 4/5 or 5/5) could be expected 37% of the time just by chance (ignoring the near zero case). With nine models the equivalent figure for n-1 is only 3.5%, and it is still much lower for n-2 (18%)... (assuming that my somewhat rusty probability calculations are correct). It really depends on what we had understood the purpose of the criterion to be. I am not certain how much this was discussed. Also, I would prefer Friday night as well if it means that more information will be available. Cheers Peter -----Original Message----- From: Hans von Storch [mailto:Hans.von.Storch@gkss.de] Sent: Wednesday, 13 September 2000 19:48 To: Congbin Fu; GIORGI FILIPPO; Bruce Hewitson; Mike Hulme; Jens Christensen; Linda Mearns; Richard Jones; Hans von Storch; Peter Whetton Subject: n-1 / n-2 Dear friends, I have already indicated that I favour the n-1 version. Obviously, this choice is arbitrary, but it was made BEFORE we did the analysis. By changing the criterion AFTER we have seen the data, we may be targeted by critics for biased rules. Using material, which is unpublished and unreviewed is already a bit shacky (Hans Oerlemans is unwilling to participate in the IPCC process because of a similar incident in the 1995 report!). Hans -- Hans von Storch Institute of Hydrophysics GKSS Research Center, Max-Planck-Strasse 1, PO Box, WWW: http://w3g.gkss.de/G/Mitarbeiter/storch/ e-mail: storch@gkss.de and storch@dkrz.de Phone: + 49 / 4152 87 1831, fax: + 49 / 4152 87 2832 privat fax: + 49 / 4153 582 522