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Commentary on the first game by Rob van Zeijst

Posted: Thu Feb 06, 2014 3:57 pm
by daal
This match has inspired yet another great commentary, this one by Rob van Zeijst. In his announcement on Facebook, he prefaced the article and commentary with: "To all Go Associations and Go Lovers: If you want to publish this article in your own language for free, it is possible, but send me an email for the conditions: rob.yourteacher[at]gmail.com or send a message to Rob van Zeijst on Facebook. Thank you"

http://www.kiseido.com/printss/guliten1.html

Re: Commentary on the first game by Rob van Zeijst

Posted: Thu Feb 06, 2014 11:03 pm
by macelee
I like the way the commentary is presented. Any idea how that web page was generated?

Re: Commentary on the first game by Rob van Zeijst

Posted: Mon Feb 10, 2014 6:10 am
by Knotwilg
The best argument against odd numbered game series is that, if a 6-5 win in an 11 game series suffices to declare a winner, then 1 game would be sufficient too. Here's my proof:

Let X be the better player and Y the other player. Let p be the probability that X wins a game against Y (p>0,5).
The game series has a double purpose: find out who is X, but also get a better idea about p.
Our current estimate would be Lee Sedol being X and p is determined by the 18-17 score in his favor.
At 5-5, we would still estimate Lee Sedol being stronger but p is now determined by a 23-22 score in his favor.
If Lee Sedol wins 6-5, he clinches the title while the probability that they are actually of equal strength, or even Gu is slightly stronger, is higher than if Lee Sedol would win 1-0.

So it would be fairer to make Lee decisively stronger after 1-0 than after 6-5.
With 6-4 it's all different. Now the probability that Gu is better, given 24-21, is lower than given 19-17.

Similarly, it would be unfair to give Gu the title at a 6-5 win (being an overall 23-23 tie), than at a 1-0 win (18-18 tie), because chances they're equal are even increased after the 11 game series.

An even jubango only yields a winner if there are at least 2 games difference. The difference between the probabilities to indicate a wrong winner in the 6-4 case and the 6-5 case is quite high.