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Subject: Re: how not to calculate performance

Author: Sune Fischer

Date: 03:39:59 11/04/04

Go up one level in this thread


On November 03, 2004 at 18:40:18, James T. Walker wrote:

>On November 02, 2004 at 19:17:19, Sune Fischer wrote:
>
>>On November 02, 2004 at 16:44:17, James T. Walker wrote:
>>
>>>On November 02, 2004 at 08:22:10, Sune Fischer wrote:
>>>
>>>>On November 02, 2004 at 07:42:24, James T. Walker wrote:
>>>>
>>>>>Just plot a graph with 999 data points all with a value of zero.  Then plot
>>>>>another graph of 1000 data points  all with a value of zero.  Then compare the
>>>>>difference.
>>>>>Jim
>>>>
>>>>Ratings can become negative, so zero is not the lowest rating possible you can
>>>>get. Zero is actually an arbitrary number you just picked out of nowhere, you
>>>>might as well have said -1000.
>>>>
>>>>The proof of this is easy, even without knowing the formula. Just consider the
>>>>1400 guy and someone who is 400 ELO weaker, then consider one that is 400 ELO
>>>>weaker than him and so on, you quickly get negative ratings.
>>>>
>>>>I don't know what the lowest rating is, even if you assume perfectly worst play
>>>>your opponent might also be playing perfectly bad or close enough to that so you
>>>>don't lose every time.
>>>>You can thus never get an expected score of 0 and an equivalent rating of
>>>>-infinity.
>>>>
>>>>-S.
>>>
>>>What is your point?
>>
>>To inform you that zero is arbitraty value, and that it isn't constant because
>>even if his rating is 0 his expected score will be higher than 0.
>>So he will lose rating if he doesn't score anything.
>>
>>-S.
>
>The zero I mentioned was not arbitrary at at all.  It was not a rating but a
>score of a game (0/.5/1.0).  Nobody in the USCF has a rating less than 100
>because that is the rating floor for all.  So I still don't see the point of
>your ramblings.
>Jim

Sorry, you have to ask someone else to explain it to you then, I cannot do it
any better.

-S.



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