3 ms·

I have no problem believing that there is match-fixing in tennis, especially among the non-elite ranks. However, it is still an extraordinary claim, and as suc

by te 11y ago

I have no problem believing that there is match-fixing in tennis, especially among the non-elite ranks. However, it is still an extraordinary claim, and as such, requires extraordinary evidence. They have examined a dataset that includes match losses by 1,509 unique players. Among others, they have accused a fellow whose match results, by their own estimation, are 4.7% likely to have occurred by chance. If you're going to be involved in throwing around accusations of this magnitude, I'd like a little more rigor in the statistics. I don't know how they sleep at night.

jib 11y ago
Yep. "Assuming the initial odds are right, these guys may have cheated". That's one hell of an assumption. The odds moving is one of the strongest indicators of the initial odds not being right. Market efficiency etc.
- phillc73 11y ago
  Is the market truly efficient? Value betting is all about finding when it's not.
  - SolarNet 11y ago
    Iff NP=P.
cjensen 11y ago
Including the 4.7% in the list really stands out. Given that the number of professional tennis players in the world exceeds 100/4.7 that sure looks like it should have been rejected due to the green jelly bean fallacy. [1] [1] https://xkcd.com/882/ https://xkcd.com/882/
notahacker 11y ago
Yup, looking at these stats puts a different complexion on the attitude of the tennis authorities (which in the case of the Davydenko-Arguello match screamed "cover up") If someone announces to you that they've done some statistical analysis of 1500 players and they were shocked to find that a few of them of them fail a suspicion test at a 95% confidence threshold, you're going to question their grasp of statistics at least as much as the players' integrity. And that's before you start considering that the "suspicious movement" flag they've chosen is a starting point for investigation by bookmakers rather than a sure indication of something being probably wrong, and their methodology for correcting outlying mispriced odds which differ from other bookmakers is laughably inadequate. Have a bookmaker whose opening price is 9.99 points longer than the average for the other bookies whose price correction moves it to 0.01 shorter than the other bookies? That's "suspicious", apparently. And that's just looking at it from a pure statistics perspective and not assessing context which might exonerate them. One of the listed names is a Grand Slam winner who [coincidentally] played his last single game this week to a rapturous crowd, and earned >$20M in prize money over the course of the career. It's possible he augmented that by throwing the odd match for 100k, but far more plausible his odds moving all over the place were the result of his form and injuries being all over the place in the latter part of his career. (For the more forensic approach into Lleyton Hewitt's "suspicious" odds movements, someone wrote this: http://www.sportdw.com/2016/01/tennis-fixing-buzzfeed-hewitt-innocent.html http://www.sportdw.com/2016/01/tennis-fixing-buzzfeed-hewitt... )
xanados 11y ago
I think you are significantly overstating the extraordinariness of these claims. People are entitled to their own priors, I suppose, but if someone asked "What is the probability that there is at least one player that has taken money to lose a match in Tennis" if you answered something less than 1% you are probably being far too trusting. It doesn't take that much evidence to turn 1% probability to 80% probability. I also don't understand why you're focusing on the 4.7% player. You have to set the cutoff somewhere, and it's not like they specifically named Michael Russell. The accusations in this case do not have much magnitude. People are accused of cheating all the time, and the evidence in this case is as strong as in other cases. Edit: On further thought, you are probably saying that the people who published this Medium post are being irresponsible publishing the names. That's a little different than I was thinking, and more reasonable I think. That said, I don't think Michael Russell is in much risk here professionally, unless this statistical analysis is much more iron-clad than I expect it to be.
deleted 11y ago
[deleted]

by te 11y ago

jib 11y ago

Yep. "Assuming the initial odds are right, these guys may have cheated". That's one hell of an assumption. The odds moving is one of the strongest indicators of the initial odds not being right. Market efficiency etc.

phillc73 11y ago
Is the market truly efficient? Value betting is all about finding when it's not.
- SolarNet 11y ago
  Iff NP=P.

cjensen 11y ago

Including the 4.7% in the list really stands out. Given that the number of professional tennis players in the world exceeds 100/4.7 that sure looks like it should have been rejected due to the green jelly bean fallacy. [1] [1] https://xkcd.com/882/ https://xkcd.com/882/

notahacker 11y ago

Yup, looking at these stats puts a different complexion on the attitude of the tennis authorities (which in the case of the Davydenko-Arguello match screamed "cover up") If someone announces to you that they've done some statistical analysis of 1500 players and they were shocked to find that a few of them of them fail a suspicion test at a 95% confidence threshold, you're going to question their grasp of statistics at least as much as the players' integrity. And that's before you start considering that the "suspicious movement" flag they've chosen is a starting point for investigation by bookmakers rather than a sure indication of something being probably wrong, and their methodology for correcting outlying mispriced odds which differ from other bookmakers is laughably inadequate. Have a bookmaker whose opening price is 9.99 points longer than the average for the other bookies whose price correction moves it to 0.01 shorter than the other bookies? That's "suspicious", apparently. And that's just looking at it from a pure statistics perspective and not assessing context which might exonerate them. One of the listed names is a Grand Slam winner who [coincidentally] played his last single game this week to a rapturous crowd, and earned >$20M in prize money over the course of the career. It's possible he augmented that by throwing the odd match for 100k, but far more plausible his odds moving all over the place were the result of his form and injuries being all over the place in the latter part of his career. (For the more forensic approach into Lleyton Hewitt's "suspicious" odds movements, someone wrote this: http://www.sportdw.com/2016/01/tennis-fixing-buzzfeed-hewitt-innocent.html http://www.sportdw.com/2016/01/tennis-fixing-buzzfeed-hewitt... )

xanados 11y ago

I think you are significantly overstating the extraordinariness of these claims. People are entitled to their own priors, I suppose, but if someone asked "What is the probability that there is at least one player that has taken money to lose a match in Tennis" if you answered something less than 1% you are probably being far too trusting. It doesn't take that much evidence to turn 1% probability to 80% probability. I also don't understand why you're focusing on the 4.7% player. You have to set the cutoff somewhere, and it's not like they specifically named Michael Russell. The accusations in this case do not have much magnitude. People are accused of cheating all the time, and the evidence in this case is as strong as in other cases. Edit: On further thought, you are probably saying that the people who published this Medium post are being irresponsible publishing the names. That's a little different than I was thinking, and more reasonable I think. That said, I don't think Michael Russell is in much risk here professionally, unless this statistical analysis is much more iron-clad than I expect it to be.

deleted 11y ago

[deleted]