“Decision: case of using computer assistance in League A”

[EdLee]

The lottery fallacy is well known.

Hi Bill, is this it ?
Or perhaps this.

[Bill Spight]

The lottery fallacy is well known.

Hi Bill, is this it ?
Or perhaps this.

Well, it's not the gambler's fallacy. (Actually, there are two gambler's fallacies, which are opposites. )

The prosecutor's fallacy sounds like it, but at least one form of the prosecutor's fallacy lies in ignoring background knowledge (probabilities).

Here is a link to a statement of the lottery fallacy. http://lucidphilosophy.com/18-lottery-fallacy/

[Gobang]

The most plausible argument to me in all this is the opinion of a player. I know what it feels like to play someone 2 stones weaker than I am and what it feels like to play with someone who is 2 stones or more stronger. There is no mistaking the difference. I am nowhere near 6d, but at that level the difference between 4d and 6d+ must be as clear as day and night. If a 6d player says that Metta cheated, then I think he probably did. The opinion of a 6d holds more weight to me than some comparison between Metta's moves and Leela's suggestions.

Lukan: "I have found another simple reason, why Carlo should be unseated from EGC main referee's position. The Italian side experssed, that he is depressed and afraid to speak on public. Following this logic, will not he be afraid to speak on public also on EGC, where he has to control 1000 players?"

How can it be that he still wants to be a referee?

Simba: "- I won't touch PGETC again if he isn't convicted and thrown out as per the rules, nor will apparently the entirety of Serbia based on what someone said a few pages ago, and I'm sure a few other strong players won't either. If the officials would rather keep this cheater in exchange for a bunch of legitimate players, then that's a shame but it's their prerogative."

Perhaps players who care about PGETC should get together and encourage PGETC to reform and legitimize itself and somehow recover from the damage caused by this debacle.

[Bill Spight]

The most plausible argument to me in all this is the opinion of a player. I know what it feels like to play someone 2 stones weaker than I am and what it feels like to play with someone who is 2 stones or more stronger. There is no mistaking the difference.

A four stone difference is perceptible. But the variability in results is also large.

If a 6d player says that Metta cheated, then I think he probably did.

Skill at go is not the same as skill in cheating detection. Hardly anybody has been trained it that. We are learning, however.

[RobertJasiek]

the difference between 4d and 6d+ must be as clear as day and night

As I have explained in forum/viewtopic.php?p=232862#p232862 , it is not clear at all for only one game or a few games. It is only clear for many played games.

[Bojanic]

Actually, focusing on the top choice is the most sensitive measure of agreement with Leela. Adding other choices makes the statistics look impressive, but also makes them less sensitive.

Edit: Yes, I know that Frejlak is not making a statistical argument.

This sensitivity might be a problem if we compare it to nothing. If we compare it to other game in same criteria, it is not.

Also, focusing just on A and numbers has another drawback - A is most common forced move - in one analyzed game there was more than 20% of such moves.

Edit: I also did not make statistical argument.

[Gobang]

the difference between 4d and 6d+ must be as clear as day and night

As I have explained in forum/viewtopic.php?p=232862#p232862 , it is not clear at all for only one game or a few games. It is only clear for many played games.

I don't agree, and I am old enough to know that something is not necessarily true, just because someone thinks he has "explained" it.

[jlt]

Winning statistics are available on the website http://www.europeangodatabase.eu/EGD/winning_stats.php

Between Jan. 2003 and June 2018,

between a 1d and a 5d, the 1d won 6.5 % of the time.
between a 2d and a 6d, the 2d won 3.7 % of the time.
between a 3d and a 7d, the 3d won 1.5 % of the time.

[Uberdude]

There is an easy way to test the claim of people who say it is easy to distinguish a 4d and 6d. Someone picks some 4/6d games, removes identifying information and shows them to these people. They then have to say which players were 4d and which 6d. How many correct will they get. This thread could do with less talking and more testing.

maf's site https://kyudan.net is a good way to demonstrate your skill (or lack thereof) of judging player ranks from play. I look forward to seeing some familiar usernames at the top of the leaderboard with average rank guess error less than 2.

Edit: I made this test at viewtopic.php?f=10&t=15832

[Bill Spight]

Actually, focusing on the top choice is the most sensitive measure of agreement with Leela. Adding other choices makes the statistics look impressive, but also makes them less sensitive.

Edit: Yes, I know that Frejlak is not making a statistical argument.

This sensitivity might be a problem if we compare it to nothing. If we compare it to other game in same criteria, it is not.

Also, focusing just on A and numbers has another drawback - A is most common forced move - in one analyzed game there was more than 20% of such moves.

Actually, that's a plus, not a drawback. If the move is forced, the player and Leela should almost always agree. Counting B or C as a match when the move is forced is problematic.

[Bojanic]

Bill,
I think that in Metta-Kim game is a B forced move. Player can answer on two similar places.

[Charlie]

Winning statistics are available on the website http://www.europeangodatabase.eu/EGD/winning_stats.php

Between Jan. 2003 and June 2018...

To save everyone, here, the effort of the long query-time over at the EGD:

Out of 4505 even games in the same time period, a weaker 4-dan player defeated their stronger 6-dan opponent 14.4% of the time.

Anyone who thinks that 14.4% is "rare" or argues that a sample of 4505 data is anything but statistically significant needs to encounter a clue at high velocity. I suppose one could argue that the data are skewed or biased or downright erroneous but doing so would constitute an own-goal: it would render the ranks meaningless and the whole question of whether a 4-dan victory against a 6-dan opponent is exceptional or not would become moot.

[Uberdude]

Charlie, I think it is fair to point out that if a 4d plays a 6d in a McMahon tournament then (with some dependence on the level of the bar) there is a bias in that the 4d was more likely in good form and the 6d poor form for them to be drawn together. So maybe an average 4d beats an average 6d only 10% not 14% but I agree neither of those are rare.

[Charlie]

Charlie, I think it is fair to point out that if a 4d plays a 6d in a McMahon tournament then (with some dependence on the level of the bar) there is a bias in that the 4d was more likely in good form and the 6d poor form for them to be drawn together. So maybe an average 4d beats an average 6d only 10% not 14% but I agree neither of those are rare.

You're right about the bias induced by McMahon but, without digressing too far down this tangent, I'd still argue that 14.4% is correct because our definitions of "4-dan" and "6-dan" are based on the same data -- mostly from McMahon tournaments, surely. In fact, the McMahon draws would also be based on that data.

Perhaps it is true that a "true 4-dan" defeats a "true 6-dan" less than 14.4% of the time but to test that hypothesis, we would have to record decades of data from tournaments that use a mode that does not induce a bias. Within such an "ideal" system, however, both Metta and Ben-David may end up with different ranks.

[Uberdude]

On the "It's easy to tell a 4 dan from a 6 dan" issue, I made a little test here, can you figure out the players' ranks? viewtopic.php?f=10&t=15832.