chasetb, on 2011-October-20, 17:10, said:
Could/would anyone please explain to me how you calculate Butler Rankings? I would appreciate it.
The calculuation of a Butler works as follows:
On a given board, all the table results (22 tables) are averaged (e.g 3x +980, 11x+480, 7x+450, 1x-50 results in (3x980+11x480+7x450-50)/22 = 514.55). This average is rounded to the nearest multiple of 10 (+510). This is called the
datum score or
datum.
Now, all results are IMPed against the datum:
The NS pairs at the tables with a result of +980 get 980-510 = 470 which converts to +10 IMPs. EW get the complement: -10 IMPs.
At the tables with a result of +480, NS get 480-510 = -30 or -1 IMP.
At the tables with a score of +450, NS score 450-510 = -60 or -2 IMP.
At the table with a score of -50, NS score -50 - 510 + -560 or -11 IMP.
In this way, every pair gets an IMP score on every board. The scores that are reported in the ranking are the
IMPs per board, i.e. the number of scored IMPs divided by the number of boards one has played.
Sometimes. the extreme scores are thrown out of the calculation of the datum score.
In addition to the arguments that some have given (it's a team game, rather than a pair game) there are other reasons why I don't like Butler scoring. In my opinion, it is a fundamentally unsound method to calculate an IMP pairs score. The Cross IMP method is much better. (In this method your score is IMPed against the scores at all other tables. Then the resulting IMPs are averaged to obtain an IMP score, which therefore can be a fraction.)
I hope this explained, in short, how Butler works.
Rik
I want my opponents to leave my table with a smile on their face and without matchpoints on their score card - in that order.
The most exciting phrase to hear in science, the one that heralds the new discoveries, is not Eureka! (I found it!), but Thats funny
Isaac Asimov
The only reason God did not put "Thou shalt mind thine own business" in the Ten Commandments was that He thought that it was too obvious to need stating. - Kenberg