Search found 430 matches

by Brian Valentine
Thu May 21, 2009 3:17 pm
Forum: Grading Debate
Topic: GRADING ANOMALIES
Replies: 565
Views: 74008

Re: GRADING ANOMALIES

Roger, The non linearity is because the performance is made up of variance in the result and variance in the samples to obtain both published grades. These variances are broadly independant, hence to observed difference follows the square root of the combined variances. The other trends you mention ...
by Brian Valentine
Thu May 21, 2009 2:01 pm
Forum: Grading Debate
Topic: GRADING ANOMALIES
Replies: 565
Views: 74008

Re: GRADING ANOMALIES

Roger, I missed your second post. The issue is quite deep and I will need to work on a short response. The essential feature that causes the effect is that all grades are based on a random performance and should be right only on average. But if a published 200 grade player plays a published 175 then...
by Brian Valentine
Thu May 21, 2009 1:46 pm
Forum: Grading Debate
Topic: GRADING ANOMALIES
Replies: 565
Views: 74008

Re: GRADING ANOMALIES

Roger, I am almost in agreement. My maths (as posted) suggest that stretch will exist and that therefore the "incorrect" grades will not be "corrected". They might have "improved" stretch compared to the old grades, but stretch will appear. If it could have been recognised that stretch is a feature ...
by Brian Valentine
Thu May 21, 2009 12:38 pm
Forum: Grading Debate
Topic: GRADING ANOMALIES
Replies: 565
Views: 74008

Re: GRADING ANOMALIES

Robert, I doubt that we are going to reach an agreement on this. I think that the logistic curve fit has to be substantially superior to the linear approach as simple systems are better understood and accepted. It is possible that the logistic curve is better at the extremes. However most games are ...
by Brian Valentine
Wed May 20, 2009 6:57 pm
Forum: Grading Debate
Topic: GRADING ANOMALIES
Replies: 565
Views: 74008

Re: GRADING ANOMALIES

I think that the chessbase debate on ratings is even more relevant to this ecf thread. For instance Robert's assertion on the logistic curve is not universally accepted. see:http://www.chessbase.com/newsdetail.asp?newsid=562. I think that the adjustment curve is a very small part of the perceived is...
by Brian Valentine
Tue Apr 28, 2009 3:21 pm
Forum: Grading Debate
Topic: GRADING ANOMALIES
Replies: 565
Views: 74008

Re: GRADING ANOMALIES

My view is that the system needs review every 2 or 3 years to make minor changes. I agree with this. Given we are stuck with ECF for the moment, my only interest is trying to get it to work. This requires some thoughts on how the review might proceed next time. All these systems have the underlying...
by Brian Valentine
Mon Apr 27, 2009 7:32 pm
Forum: Grading Debate
Topic: GRADING ANOMALIES
Replies: 565
Views: 74008

Re: GRADING ANOMALIES

Michael, Thank you for taking the time to look at my calculations. I accept that my estimates are "hopeful" or even something less charitable. Given the small samples of results for many players and the plausibly inherent stability in each player's grade (eg Juniors or even "cycles" mentioned in thi...
by Brian Valentine
Fri Apr 10, 2009 1:53 pm
Forum: Grading Debate
Topic: GRADING ANOMALIES
Replies: 565
Views: 74008

Re: GRADING ANOMALIES

This debate has often referred to reasons why stretch might have occurred. Given I believe that stretch of some sort will always exist, is there any evidence that shows such stretch has been different in earlier times? It is clear it has existed in 2000+, but is there any firm evidence that there ha...
by Brian Valentine
Sun Apr 05, 2009 12:53 pm
Forum: Grading Debate
Topic: GRADING ANOMALIES
Replies: 565
Views: 74008

Re: GRADING ANOMALIES

This note should be considered as the first step in a line of enquiry. I believe, but cannot prove yet, that many of the grading impurities discussed in this forum will explain more of the observed stretch. I aim to set out that any the variance in the system will lead to “stretch” and generally...
by Brian Valentine
Sun Apr 05, 2009 8:21 am
Forum: Grading Debate
Topic: GRADING ANOMALIES
Replies: 565
Views: 74008

Re: GRADING ANOMALIES

I realise this contribution is far too late to influence the latest review of grades, but I would like to lay down a marker for the next investigation into the “grading stretch” issue. In announcing the grading meeting for last October Dave Thomas stated: ‘Players who outgraded their opponents...