4NCL Online

[John Reyes]

Mick,
I don't know the answer to that question, but the captains were told that those detected as cheating were spread across the divisions and that there wasn't a noticeable bulge anywhere. The evidence that I have seen would bear this out, but that may be because I am only aware of a certain subset of cases.
Matt

The question is how many players have been caused on Lichess and in what divisions etc?

[JustinHorton]

Do we have any statistics comparing the results of games played by players X hundred points apart at different positions on the scale?

We have a letter from Regan a few years ago:

"In the training set drawn from the years 2006–2009, players with Elo rating between 2190 and 2210 matched Rybka 3’s top move 48.3%, those with ratings between 2290 and 2310 matched 50.4%, and those between 2690 and 2710 matched 56.3%."

and

"[Borislav Ivanov's] observed move-matching [was] 69.6% overall, 69.0% after excluding book moves. With the settings for 2300 (2339), on the included positions with Ivanov to move, my analyzer projects 53.2% matching, ... For 2200 (2233) the projection is 51.9% ... . With the 2700-player settings, the projection moves up to 58.5% ...."

Thanks for this, but I think you may be answering a question I did not ask.

[Michael Farthing]

Michael: I don't know whether the distribution used by Ken Regan (for move matching rates) is normal. But here I don't think this is key, because what matters is the probabilities of rare events, and given he has analysed pretty much every major tournament that ever existed (or claims to) he can take his distribution directly from data - what really matters is how much something is an outlier, not whether the distribution is normal.

My use of 1-sigma, 2-sigma refers more to the probabilities they represent, and less to a claim as to whether the distribution of move-matching is normal.

But in terms of performance fluctuations, I do think one can regard 2 sigma fluctuations *in underlying strength* as much easier than they actually are. In reference to another thread, a real 2400 even if drunk, unprepared and suffering with flu does not play like a 1200. Magnus Carlsen even when actually drunk is still one of the few best bullet players in the world (DrDrunkentstein).

If we take 25 ECF, or 200 ELO, as a standard deviation in playing strength, the claim that there are players with stable ratings who can fluctuate on their raw strength by 2 standard deviations between tournaments is equivalent to the claim that there are stable 2200s who - when they are on form - could be expected to hold their own in e.g. the Grand Swiss and get 50% or better. Personally I do not believe this for a moment.

Certainly one needs appeals processes with experienced humans; but 4 sigma - 1in 30,000 - performances really are extraordinary and should be scrutinised.

Joseph

My comments were not really about the substantive questions but pointing out that you cannot make predictions about an individual based on the cumulative behaviour of a population. It was a technical point about your particular example and should not be seen as having more significance than that. In particular you cannot use a 1-sigma or 2-sigma to refer to probabilities unless the distribution is known and certainly not for making predictions about an individual where particular circumstances may distort the pattern of results.

We are agreed that where there are outliers it is reasonable to look for causes that explain their presence - however, there may be many of these. In the case of Knightie (as augmented and imagined by me), should his performance have been outlying, two such causes have been suggested which I give give below in decreasing order of likelihood (in my opinion) (and yours):

1. Knightie was cheating
2. Knightie had personal difficulties that led him to have highly erratic performances (though insufficient to trigger an accusation of the strength being considered in the thread as a whole).

Enough said. Personally I'd much prefer you to start a new thread giving a slightly but not overwhelming mathematical introduction to string theory. Most accounts are either impossible to penetrate or rather crude attempts to give analogies that actually shed no light at all. Sadly, there might not be many other forumites interested.

[Roger de Coverly]

In the case of Knightie (as augmented and imagined by me), should his performance have been outlying, two such causes have been suggested which I give give below in decreasing order of likelihood (in my opinion) (and yours):

1. Knightie was cheating

Also he or she might have been attempting to maintain a rating or grade at a level sufficient to pick up prizes in restricted tournaments.

[Brian Valentine]

Do we have any statistics comparing the results of games played by players X hundred points apart at different positions on the scale?

The information is in this article:https://en.chessbase.com/post/what-s-wr ... elo-system

[NickFaulks]

The information is in this article:https://en.chessbase.com/post/what-s-wr ... elo-system

Yes, it was pointed out to Jeff that ENG, which provided his example, is not a typical federation. To be fair, there are others which aren't typical either.

[Alex McFarlane]

ENG, which provided his example, is not a typical federation.

Come on, Nick. You are no longer allowed to say something is not typical without providing a sigma number to back up your assertion!

There then follows 173 pages of discussion debating whether that figure is significant or not

[MartinCarpenter]

I think, in the case of low ELO ratings in the UK, its surely very safe to say ‘badly messed up, don’t use for detailed statistics’

If we wanted a discussion it might be about whether ECF ratings are quite stable enough to use instead....
(They’ve been messed around several times recently of course.).

[Nick Grey]

1A to 20Y Best No sigmas.

[John Reyes]

the question is how do we improved if there is a 2nd season?

the 4ncl is the flagship of british chess and it is down to everyone to support it

[IM Jack Rudd]

the 4ncl is the flagship of british chess

I think the British Championships might take issue with that description.

[John McKenna]

Then might one say that the British Championships are the flagship, and 4NCL the main battleship, of British Chess!?

[DavidWalker]

Suppose chess player Knightie McKnightFace plays six tournaments a year and has a stable rating...

A stable rating is the key assumption, but suppose that Knightie has had more free time available recently and has been working much harder than usual on their game. As a consequence their playing strength has increased over the course of a season.

Suppose Knightie's average yearly ECF grade over the past 20 years is 210, with a standard deviation (SD) of 4 points. This means that most of the time their published grade would vary between 206 and 214, but values of 202 and 218 would not be unexpected. I think this is a plausible range of grades based on my own experience (in particular between 1994 and 2013. This does assume that the effect of 2009 new grades is relatively small in this grading band).

Suppose that Knightie's work pays off and their rating increases to 230 (again similar to my own experience). This represents a 5 sigma deviation from the previous average. However, this does not mean that anything tremendously unlikely has happened. What it does mean is that it is very unlikely that Knightie's increased rating is solely due to chance but instead is due at least in part to the extra work put in.

The key point is that a very high z-score does not necessarily relate to an implausibly high change in rating.

[Matthew Turner]

David,
I don’t really understand what you are trying to say here. For Ken Regan’s test the standard deviation is based on the entire population. So if knightie is 206 that is 2245 and he would have to select engine moves at a rate associated with a player rated 3045 to get a z score of 4.
Matt

[Nick Grey]

Big improvement ban cheats and suspects season 2.