Re: Don't Understand Grading Calculation
Posted: Mon Oct 21, 2019 9:37 am
I would ask the 200 how well his opponent played and provide an informal estimate of grade.
The independent home for discussions on the English Chess scene.
https://www.ecforum.org.uk/
Then you have to know whether the 200 is the kind who thinks every game they win a Herculean effort worthy of a candidates' tournament, or the kind who assigns everyone below 195 to the same "idiot" category.Kevin Thurlow wrote: ↑Mon Oct 21, 2019 9:37 amI would ask the 200 how well his opponent played and provide an informal estimate of grade.
Well what happens in league chess is that they play a few stronger people, you get a decent estimate and they're stuck on a realistic (if often slightly conservative) board. The strength of their teammates on either side is arguably more useful data than their opposition but using that would be slightly odd I guess.Chris Goodall wrote: ↑Mon Oct 21, 2019 9:23 amLet's apply your logic from the other direction. A player walks into your club and claims to be from a country you were sure was still part of Russia. You put him on board 5 in Division 3, and he easily beats a couple of children graded 38 and 49. Do you therefore let him enter the Under 100 section of your congress, because the fact that he played against those children makes him a weaker player than if he hadn't?
Why is that odder than using their opponent's strength?MartinCarpenter wrote: ↑Mon Oct 21, 2019 5:48 pmWell what happens in league chess is that they play a few stronger people, you get a decent estimate and they're stuck on a realistic (if often slightly conservative) board. The strength of their teammates on either side is arguably more useful data than their opposition but using that would be slightly odd I guess.
If those were his only results and the ECF included estimates on 2 games at the next grading date he would be (98+109)*.5 = 104, provided the junior grades stayed at 38 and 49, so you probably wouldn't let him play in an U100 event.Chris Goodall wrote: ↑Mon Oct 21, 2019 9:23 amA player walks into your club and claims to be from a country you were sure was still part of Russia. You put him on board 5 in Division 3, and he easily beats a couple of children graded 38 and 49. Do you therefore let him enter the Under 100 section of your congress, because the fact that he played against those children makes him a weaker player than if he hadn't?
140 actually, at the next grading date.in connection with another point Chris Goodall wrote: ↑Sun Oct 20, 2019 8:35 pmIf I were the ECF, my estimate of his grade would jump up to 150!
So the fact that they found themself sitting opposite a certain person is 40 percentage points' worth of information, and the fact that they lost is only 17?Brian Valentine wrote: ↑Tue Oct 22, 2019 2:55 pmIsn't Martin suggesting that the player moves up to say 90th percentile when they start the game with the locational extra information and they drop to 73 when the additional information of the result becomes available?
Clarke has always been OpptAverage - 50 + %pt score, has that 50 changed to 40 without me noticing?E Michael White wrote: ↑Wed Oct 23, 2019 1:16 pmIf those were his only results and the ECF included estimates on 2 games at the next grading date he would be (98+109)*.5 = 104, provided the junior grades stayed at 38 and 49, so you probably wouldn't let him play in an U100 event.Chris Goodall wrote: ↑Mon Oct 21, 2019 9:23 amA player walks into your club and claims to be from a country you were sure was still part of Russia. You put him on board 5 in Division 3, and he easily beats a couple of children graded 38 and 49. Do you therefore let him enter the Under 100 section of your congress, because the fact that he played against those children makes him a weaker player than if he hadn't?
140 actually, at the next grading date.in connection with another point Chris Goodall wrote: ↑Sun Oct 20, 2019 8:35 pmIf I were the ECF, my estimate of his grade would jump up to 150!
Oddly at the other extreme things seem to work a little better. If an ungraded player plays 15 players graded 140 and scores 100% he would be graded as 200. Doesn't seem that bad as an estimate.
Both 140 and 150 are right in their own way.Chris Goodall wrote: ↑Wed Oct 23, 2019 3:41 pmClarke has always been OpptAverage - 50 + %pt score, has that 50 changed to 40 without me noticing?E Michael White wrote: ↑Wed Oct 23, 2019 1:16 pm[140 actually, at the next grading date.in connection with another point Chris Goodall wrote: ↑Sun Oct 20, 2019 8:35 pmIf I were the ECF, my estimate of his grade would jump up to 150!
Isn't this what used to happen before the central computer program took over the job of working out what a new player's grade should be? (Except there was then no iteration because there was no program.) Local graders' estimates were usually accurate to within 10 points or so, I recall.Angus French wrote: ↑Wed Oct 23, 2019 3:39 pmWhy not ask leagues and congresses, through their results officers, to provide estimates which could then be used as seed values ...
Mike Gunn wrote: ↑Wed Oct 23, 2019 4:12 pm
Isn't this what used to happen before the central computer program took over the job of working out what a new player's grade should be? (Except there was then no iteration because there was no program.) Local graders' estimates were usually accurate to within 10 points or so, I recall.
Local graders' estimates are subject to confirmation bias - they'll remember the ones they got right. I'd be surprised if they're not biased towards boring percentage chess too. A player loses to me with the Latvian Gambit, I'll estimate his grade at 120. Then he beats me with the Blackmar-Diemer, and I'll revise my estimate down to 90Roger de Coverly wrote: ↑Wed Oct 23, 2019 4:55 pmMike Gunn wrote: ↑Wed Oct 23, 2019 4:12 pm
Isn't this what used to happen before the central computer program took over the job of working out what a new player's grade should be? (Except there was then no iteration because there was no program.) Local graders' estimates were usually accurate to within 10 points or so, I recall.
They could "cheat" of course, by waiting until they had a decent set of results before making an estimate. The other convention was to assume players had a grade of 100 in the absence of any other information.
It was only after the advent of automatic estimates that the problem of negative grades started to appear.