Am I just unfortunate?

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IM Jack Rudd
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Re: Am I just unfortunate?

Post by IM Jack Rudd » Fri Jan 23, 2015 7:59 pm

The probability of your getting a result at least that extreme in either direction from 28 events is about 1.2%. Given the number of people who play weekend congresses at that sort of rate, there must be quite a lot of people with a similar distribution.

David Robertson

Re: Am I just unfortunate?

Post by David Robertson » Fri Jan 23, 2015 8:16 pm

Before each event, present a large pie to the arbiters. Your luck will soon change.

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David Shepherd
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Re: Am I just unfortunate?

Post by David Shepherd » Fri Jan 23, 2015 8:46 pm

I was trying to work out in my head whether, given the rule about the higher graded player keeping the colour sequence, the probability of getting white and black is equal or whether any/all of: grade relative to field, results playing black compared to white, results against lower/higher graded player had an impact.

Rapidly starting to get a headache :(

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IM Jack Rudd
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Re: Am I just unfortunate?

Post by IM Jack Rudd » Fri Jan 23, 2015 8:48 pm

David Shepherd wrote:I was trying to work out in my head whether, given the rule about the higher graded player keeping the colour sequence, the probability of getting white and black is equal or whether any/all of: grade relative to field, results playing black compared to white, results against lower/higher graded player had an impact.

Rapidly starting to get a headache :(
I'm not surprised. I'd hazard a guess that that sort of thing is best solved by Monte Carlo methods.

LawrenceCooper
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Re: Am I just unfortunate?

Post by LawrenceCooper » Fri Jan 23, 2015 8:52 pm

Paul Georghiou wrote:
So am I just unfortunate? Or is something else going on? And should something be done about it?
Well you had white in your only game against me, not sure if you managed more whites or blacks in the tournament though :lol:

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Christopher Kreuzer
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Re: Am I just unfortunate?

Post by Christopher Kreuzer » Fri Jan 23, 2015 8:52 pm

David has already mentioned it, but I agree that being among the top seeds makes staying 'on' colour more likely. Certainly someone is getting the extra Whites! Paul, if you want to analyse further, are you able to say how common it was for you to get WW or BB sequences? And the important question: did you do better with more Blacks or Whites...?

Roger de Coverly
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Re: Am I just unfortunate?

Post by Roger de Coverly » Fri Jan 23, 2015 9:17 pm

David Shepherd wrote: given the rule about the higher graded player keeping the colour sequence
General reasoning suggests a lock-in is probable where you are more likely to go 3-2 if you have white in the first round. Being in a position to win a tournament will have a bearing, particularly in a smaller tournament as it will be necessary to meet the "only" opponent regardless of colour.

Jonathan Bryant
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Re: Am I just unfortunate?

Post by Jonathan Bryant » Fri Jan 23, 2015 10:16 pm

David Robertson wrote:Before each event, present a large pie to the arbiters. Your luck will soon change.
Being friends with the tournament controller will only go so far. A good friend of mine recently gave me a fourth black in the sixth and final round of our club’s mid-season rapidplay tournament. He seemed to think that the fact that this was the "correct" pairing was reason enough to do it.

A while back I had something like a dozen blacks in a row in club chess. That’s not quite true in that in the middle of the run I did get a white ... but my opponent didn’t turn up to that game.

Richard Bates
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Re: Am I just unfortunate?

Post by Richard Bates » Sat Jan 24, 2015 6:59 am

There could be an argument that in a tournament with an odd number of rounds, (possibly assuming where one is a strong favourite to win in round 1), it is arguably an advantage to be given black in round 1. The point being that in the remaining rounds I will have a minimum 50% of whites, with any colour switch in an odd numbered round resulting in +2 whites. The counter argument to this (black in round 1 being an advantage) is nothing to do with overall numbers of whites and blacks, but that having black in round 1 will, assuming no switches, give you black in the last round ie. the round that matters.

Alistair Campbell
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Re: Am I just unfortunate?

Post by Alistair Campbell » Sun Jan 25, 2015 1:48 pm

Going back to the OP, it strikes me there may be a touch of the toast always* landing buttered side down about this – not that I claim to be an expert (on toast, chess or probability :( ).

Clearly, if one conducts an enormous number of supposedly random trials, one is going to generate lots of supposedly unlikely sequences. Try going down to your local casino and employing the martingale system. On second thoughts, don’t do that.

However, as David pointed out, there is bias here, in that colour is not determined at random, but by Swiss pairing rules. I wonder if the original result is a consequence of in which octile (say) the player is typically seeded.

For example, the following sequences (colour; relative seeding; result) may be relatively common (I think Roger is hinting at something along these lines?) :

W; higher seed; W
B; higher seed; W
W; lower seed; D
B; higher seed; W
B; lower seed

B; higher seed; W
W; higher seed; W
B; lower seed; L
W; higher seed; W
B; higher seed;

Obviously I’ve guarded against headaches by not investing too much thought. Swisses of 7 rounds or more may even things out better. This line of thinking suggests that initial seeding may be a factor in the ultimate result in an Olympiad (well, d’oh :oops: , of course it will). Perhaps I can express that better – there seems to be an “escalator effect” – the team wins well, shoots up the rankings, loses badly, plummets down the rankings. Initial seeding will determine in which round it is likely you receive your first thrashing, triggering the escalator.

*apparently this is something to do with the relationship between the dimensions of a typical slice of bread and the height of the typical table/counter top

Ian Thompson
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Re: Am I just unfortunate?

Post by Ian Thompson » Sun Jan 25, 2015 2:10 pm

Alistair Campbell wrote:However, as David pointed out, there is bias here, in that colour is not determined at random, but by Swiss pairing rules. I wonder if the original result is a consequence of in which octile (say) the player is typically seeded.
I could believe that there is bias in the likelihood of players maintaining an alternating colour sequence throughout an event depending on where they are seeded.

I doubt there is any bias in the likelihood of a player getting an extra Black based on seeding though. There's a 50% chance, for all players, of getting White (or Black) in round 1. If there's bias in the subsequent pairings, isn't that just going to mean that some players have a greater chance than others of maintaining an alternating colour sequence, but the chances of the switch giving them an extra Black by the end of the tournament is equal to the chances of the switch giving them an extra White by the end of the tournament?

Niall Doran
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Re: Am I just unfortunate?

Post by Niall Doran » Sun Jan 25, 2015 2:17 pm

Clive Blackburn wrote:
MartinCarpenter wrote:Getting thumped at home then chances for the away matches is actually quite liable to distort the overall results come the end of the season :)

I guess one slight counter balance would be that there does definitely tend to be a non trivial home/away effect in chess, even over and above player availability. I guess the travel must have an effect.
Yes, the travel might be tiring but there is also the fact that the home team will have an extra incentive to perform well with members of their own club watching the games.
Personally, I prefer playing away. No arriving early to open up, set up the boards, clocks, put the coffee on and so on. You just arrive and play.

Roger de Coverly
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Re: Am I just unfortunate?

Post by Roger de Coverly » Sun Jan 25, 2015 2:17 pm

Alistair Campbell wrote:(I think Roger is hinting at something along these lines?)
It would be a theory about how good a predictor your first round colour was as a determinant of your colour split. The hypothesis would be that the higher you were in the rankings, the better it became. You first round colour being determined by where you were placed in the first round rankings and the colour given to the top ranked player.

If you start with an odd numbered position in the rankings, you are more likely to meet even numbered opponents than odd numbered ones.

Paul Robson
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Re: Am I just unfortunate?

Post by Paul Robson » Sun Jan 25, 2015 2:29 pm

Hi Paul

Although this thread seems to have moved on I think the answer to your question is simply ....YES

Alistair Campbell
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Re: Am I just unfortunate?

Post by Alistair Campbell » Sun Jan 25, 2015 9:09 pm

Ian Thompson wrote:I could believe that there is bias in the likelihood of players maintaining an alternating colour sequence throughout an event depending on where they are seeded.

I doubt there is any bias in the likelihood of a player getting an extra Black based on seeding though. There's a 50% chance, for all players, of getting White (or Black) in round 1. If there's bias in the subsequent pairings, isn't that just going to mean that some players have a greater chance than others of maintaining an alternating colour sequence, but the chances of the switch giving them an extra Black by the end of the tournament is equal to the chances of the switch giving them an extra White by the end of the tournament?
I think the argument was along the lines that initial seeding would tend to determine when you could expect a “bad” result, and this could be exacerbated (or alleviated) by colour. This would then have an influence on relative seeding (and hence propensity to alternate colour) thereafter. Thus colour would also be a source of bias.

It would be interesting if the OP could give some sample stats regarding colour, seeding and result (although the sample would be pretty small).

Of course, if it could be proved that the bias was significant, similar arguments would suggest an opposite bias for another octile (if octile is the right division). However, unlike the upper end of the distribution, I think people are less likely to find themselves consistently in the 7th octile, say. So the answer to who is getting the extra whites, is probably that they are being spread out amongst almost everyone else, with the possible exception of the top seed...
Roger de Coverly wrote: It would be a theory about how good a predictor your first round colour was as a determinant of your colour split. The hypothesis would be that the higher you were in the rankings, the better it became. You first round colour being determined by where you were placed in the first round rankings and the colour given to the top ranked player.

If you start with an odd numbered position in the rankings, you are more likely to meet even numbered opponents than odd numbered ones.
Wouldn’t things be relatively symmetrical? So being bottom seed would also be a good predictor?

You are going to have to explain this last point to me…