From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 11390f,be6b7e036aa9236c X-Google-Attributes: gid11390f,public X-Google-Thread: 10261c,68666e29d0425009 X-Google-Attributes: gid10261c,public X-Google-Thread: 103376,be6b7e036aa9236c X-Google-Attributes: gid103376,public X-Google-Thread: 1094ba,be6b7e036aa9236c X-Google-Attributes: gid1094ba,public X-Google-Thread: 1014db,be6b7e036aa9236c X-Google-Attributes: gid1014db,public X-Google-Thread: 1164ba,be6b7e036aa9236c X-Google-Attributes: gid1164ba,public X-Google-Thread: 114809,68666e29d0425009 X-Google-Attributes: gid114809,public X-Google-Thread: fa0ae,be6b7e036aa9236c X-Google-Attributes: gidfa0ae,public From: dik@cwi.nl (Dik T. Winter) Subject: Re: Results of my test: Re: Friday 13th, try it yourself Date: 1996/09/27 Message-ID: #1/1 X-Deja-AN: 185625902 sender: news@cwi.nl (The Daily Dross) references: <52bmft$f3l@news1.halcyon.com> organization: CWI, Amsterdam newsgroups: comp.lang.ada,comp.lang.apl,comp.lang.basic,comp.lang.c,comp.lang.fortran,comp.lang.perl.misc,comp.lang.pascal.misc,comp.lang.smalltalk Date: 1996-09-27T00:00:00+00:00 List-Id: In article Lee Crites writes: ... > Summary of Friday dates for 400 years: ... > If I'd made a wild guess of what the results would have been before I > started, I'd have come up with something similar to the above. Uniform > distribution across all dates -- with diminished numbers from the 29th > through 31st. Yup, it looks uniform. But because these are exact figures, valid for every period of 400 years, they are *not* uniform but biased in favour of Friday 13 (and 6, 20 and 27). > Realizing these results would not make the it's-not-uniform-distribution > group happy, I ran it again based upon 1800 instead of 1753, with exactly > the same results. Which ought to have shown you that the figures are exact for every period of 400 years. The situation is similar to a pseudo-random number generator that repeats a sequence of 100 digits 0 and 1 with 49 occurrences of 0 and 51 of 1. When you look at it without background information it looks uniform, but because you know it repeats you know also that it is biased in favour of 1 and so not uniform. -- dik t. winter, cwi, kruislaan 413, 1098 sj amsterdam, nederland, +31205924131 home: bovenover 215, 1025 jn amsterdam, nederland; http://www.cwi.nl/~dik/