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Improving Swiss Teams events

#41 User is offline   Mbodell 

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Posted 2007-April-22, 19:57

jdonn, on Apr 20 2007, 12:47 PM, said:

Gerben42, on Apr 20 2007, 12:36 PM, said:

Not the best team, the team who played best in the tournament.

No, exactly what I said. Read the original post.

"We consider event formats in which the sample statistic [swiss team results] closely mirrors the population statistic [skill level or ability of the teams] superior to formats in which {this is not the case}."

That's a false issue that just has to do with applying the model to real life. Consider the population statistic that was used to be the teams raw "skill level" plus a modifier based on conditions of the day (I.e., current form). So a team that in the OP's model had been rated as a +2 team could be a +1.5 team that is "playing well" (well rested, good frame of mind, etc.) or a +2 team playing normally or a +2.5 team playing below their average skill level. Thus even if the "best team" according to the model won it doesn't necessarily translate into the best same 4 or 6 people winning.

With respect to the more general point there is a procedure for this from the Chess world where many tournaments are swiss tournaments (and in fact where swiss tournaments began) with limited rounds and a 0-1 VP scale (with .5-.5 for draws) and further constraints (have to decide W vs B color issues with the pairings). Obviously in chess tiebreakers are pretty important since with a small range of scores many players can end up tied. See swiss perfect tiebreaking site for all the methods.

The simplest method that sort of works to adjust the SoS that is even simpler than the OP is to simply take your cumulative score. This works as a proxy for your strength of schedule but is very simple to calculate since you only have to look at your own team's score. For instance if you went 20-0, 16-4, 11-10, 2-18 you would have 49 VP out of 80 but your cumulative score would be 20+36+47+49 = 152. If some other team scored 0-20, 11-9, 20-0, 18-2 they also have 49 VP but they were taking the easy side by getting blitzed in their first round and have a cumulative score of 0+11+31+49 = 91. Thus you win the tiebreak.

Of course in chess this only works as a tiebreaker, not as something that gets added to your score. And the problem in bridge swiss events is that the victory points lead to an expanded range so what if that second team was 19-1 in their 4th round match and had 50 VP. Was that a more impressive finish than the first team who played up but only ended up with 49 VP? Probably not. But if you are going to make any adjustment at the end I think you clearly also want that the same kind of bonus/adjustment to be used after each round to set up the next rounds pairings.

To the OP, what exactly was you adjustment formula? You said it depended on the number of rounds, but how did it work?
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#42 User is offline   Gerben42 

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Posted 2007-April-23, 02:43

Quote

So why do they play at all? They could just send the top seed.


This doesn't change much, now the seeding mechanism is the actual qualification (I don't know if this is such a bad idea!)

*********************

The main problem with the combination Swiss + VP is the closeness in scores. If you can only win or lose, a win in the last match will not allow anyone to overtake you, and a loss will only allow others to tie against you. My main problem is that Swissing keeps the field closer and allows teams to catch up with the leaders way too easily.

Example from Estoril transnationals. Actual final ranking after 15 rounds:

1st. 276
2nd. 270
3rd. 268
4th. 266
5th. 265
6th. 264
7th. 262
8th. 261
9th. 260
10th. 259

Average: 220

If you look however what the top 10 would've gotten against AVERAGE opponents:

1st. 308
2nd. 304
3rd. 300
4th. 296
5th. 292
6th. 291
7th. 288
8th. 286
9th. 280
10th. 278

Average: 220

Let's say you play a 16th round in each case. The chance that a lucky team reaches the top 8 (or pick 4, 16, any number) for the KOs suddenly is much greater in the 1st scenario.

Quote

I do not think making the results of swiss team events more "accurate" is a good thing. Most people seem to be taking for granted that it is.


Why do you think giving more points to teams who played well compared to teams who didn't is a bad thing? Just because we've always used Swiss?
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#43 User is offline   AlexOgan 

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Posted 2007-April-23, 07:32

jdonn, on Apr 22 2007, 11:49 AM, said:

I do not think making the results of swiss team events more "accurate" is a good thing. Most people seem to be taking for granted that it is. I am not criticizing the effectiveness or accuracy of the model itself, I'm saying I don't ever want to see it implemented (which thankfully, I doubt it will be.)

OK, then -- how about making the results of swiss team events LESS "accurate"? There are lots of adjustments we could make to format/pairing/scoring that would acheive that. Would that be a good thing? Or are you claiming that the existing system is perfect?
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#44 User is offline   TylerE 

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Posted 2007-April-23, 19:47

At least here in ACBL-land, I think the use of the 30pt VP scale would make for a fairer event. It really sucks get to a round of very non-swingy boards, outplay the opponents by an overtrick or two, and barely get credit for more than a tie.
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#45 User is offline   jdonn 

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Posted 2007-April-24, 01:25

AlexOgan, on Apr 23 2007, 08:32 AM, said:

jdonn, on Apr 22 2007, 11:49 AM, said:

I do not think making the results of swiss team events more "accurate" is a good thing. Most people seem to be taking for granted that it is. I am not criticizing the effectiveness or accuracy of the model itself, I'm saying I don't ever want to see it implemented (which thankfully, I doubt it will be.)

OK, then -- how about making the results of swiss team events LESS "accurate"? There are lots of adjustments we could make to format/pairing/scoring that would acheive that. Would that be a good thing? Or are you claiming that the existing system is perfect?

It's an impossible claim to make since it's just a matter of opinion. But I do like the current system very much. Sure people complain but people would complain about any system in use. I can't think of a single sport or game (perhaps other than those decided by voting or judging) in which either the best team always wins, or strength of schedule is taken into account in the final ranking of a single event, though it's possible there is something I don't know about that uses SOS (maybe in chess as a tiebreaker?) Simply put, if it's not broke don't fix it.

If I did have to change, I would prefer it to be less accurate compared to more accurate. A very good team (in context) tends to win swiss team events pretty consistently, albeit not always the best team. In fact I would say the odds the winning team played best that day is enormously high, purely as a gut feeling. There are very few fans of anything who would want to all but eliminate upsets (ok, maybe NY Yankee fans.) Look how wildly innaccurate a poker event is in terms of who played best that day compared to who won, the correlation is very small indeed. Is that game lacking in popularity?

Richard is right in any case that it can never hurt to understand what you are working with as best you can.
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#46 User is offline   cherdano 

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Posted 2007-April-24, 09:52

jdonn, on Apr 24 2007, 01:25 AM, said:

If I did have to change, I would prefer it to be less accurate compared to more accurate. A very good team (in context) tends to win swiss team events pretty consistently, albeit not always the best team. In fact I would say the odds the winning team played best that day is enormously high, purely as a gut feeling. There are very few fans of anything who would want to all but eliminate upsets (ok, maybe NY Yankee fans.)

In a 2-day event with 128 teams? This sounds pretty much like lottery to me. (And I understand that's where the Australians are planning to use it.) Even in a one-day K.O. match it doesn't always seem to be the better-team-on-that-day that ends up winning.

Anyway, they are only trying to make up for the unfairness of Swiss scoring, not for the 5% slams (needing two 3-3 breaks and the wrong lead) that make so there will be enough element of chance left...
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#47 User is offline   mycroft 

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Posted 2007-April-24, 10:36

I agree with a lot of things around here.

Bluejak, in another forum, has made this point, which I believe is very strong: Swiss events are popular not because they are a reliable test of current form, but because you're going to get something (chance of being Monsterpoint blitzed is very low) and because swisses are, in fact, a highly luck-based event.

If that is the case, "improving" the swiss by removing some of the luck will, in fact, decrease the popularity of the event. As others have said, how many point-a-board (board-a-match in NA) events are there any more? Why? Because if you're not the best, you can't win.

If you are trying to come up with a pre-trials method, as it seems Richard et al. are, then you want an event where the best 8 on the day out of 128 are as likely as possible to be in the top 8 of the results. In other words, exactly what the Swiss won't do.

Swiss is good for feeding out the top, the top 2; you need, supposedly, another round for each lower team you wish to rank, which leads into overswissing issues - you could avoid that by having the best and worst leave after N rounds, but the problem is that they paid (especially the worst) to play.

I would strongly suggest some sort of qualifying/consolation event, if it's over two days (if it's over 4, then my previous suggestion of 2/32, RR, applies. People may not like that as much though, if they're not expecting to make the top. There's a joy in the randomness, especially for the card-push set). From 128, qualify 64, seeded into two flights of 32, whatever carryover seems appropriate - frankly, if you want to get "the best at beating good opposition", no carryover might be right. Swiss the three events (1Q, 2Q, C); play your standard set in C (most of whom want consistency over accuracy anyway), and 6 rounds of however many boards in the two Qs. That should let xQ1 and xQ2 rise to the top, without too much overswiss. 3 and 4 in each bracket will be somewhat more of a crapshoot, but you'll have reasonable confidence that the top four teams, at least, have made it in. In the Qs, use whatever methods you like to "improve" the results of the top four; many more of them will "get it".

Note that this also helps the "get our 3/4 green" people, as the second day has weeded out most of the big fish from the consolation, and those few that get there that came to qualify may prefer the beach to playing.

Michael.
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#48 User is offline   barmar 

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Posted 2007-April-28, 22:11

jdonn, on Apr 24 2007, 02:25 AM, said:

If I did have to change, I would prefer it to be less accurate compared to more accurate. A very good team (in context) tends to win swiss team events pretty consistently, albeit not always the best team. In fact I would say the odds the winning team played best that day is enormously high, purely as a gut feeling. There are very few fans of anything who would want to all but eliminate upsets (ok, maybe NY Yankee fans.) Look how wildly innaccurate a poker event is in terms of who played best that day compared to who won, the correlation is very small indeed. Is that game lacking in popularity?

I'm not sure what makes you think the proposal would make upsets less likely. Nothing in the proposal gives any bias to teams based on their past performance. The scoring is still based just on how well they play during the event in question. I think you're confusing the simulation, which assigns rankings to the simulated teams, with how it would be used in practice -- no rankings are involved there. The rankings represent a prediction of how well the teams will play during the simulated event.

If scoring is less accurate, it means that just about anyone can win. Should bridge really be a lottery, rather than a game of skill?

What I wonder is how relevant this proposal would be to the Swiss Team tournaments that are most commonly played. How accurate is a two-session Swiss (typically 8 rounds of 7 boards in most ACBL tournaments), and how much of an improvement would there be if the SoS adjustment were made?

Regarding the comparison with poker ... I haven't watched too much poker (mostly just Celebrity Poker Showdown -- the table chatter is fun), but the impression I get is that the winner is often determined by just a few critical hands. While there's certainly skill in reading your opponents and knowing when to bluff, a lucky card when someone decides to go all in can make all the difference.
In contrast, while a slam swing can often determine the winner of a 7-board match, but it's not likely to determine the winner of the event.

#49 User is offline   bhall 

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Posted 2007-May-04, 16:25

Wouldn't it be great to replace Swiss pairing by a method that gave good estimates for the relative strength of all the top-half teams? Gerben Dirksen (Gerben42) has made a start in this direction by estimating the outcomes of unplayed matches by something like maximum likelihood.

Suppose that we could choose the pairings on each round, and the number of boards for that round's matches, based on maximizing the accuracy of our after-the-round estimates. I wonder what such a method would look like.

While it might not be popular as a replacement for the Sunday Swiss, I'll bet such a method would be embraced by national bridge organizations seeking to select their best representatives for international play. It might even give rise to unbiased, worldwide strength estimates for individuals, pairs, and teams!

No, I must be dreaming. :)
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#50 User is offline   cherdano 

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Posted 2007-May-04, 18:18

Btw, I think it would be quite worthwhile to compare this with pure win/loss scoring, VP as tie breaker, assuming that you also assign the pairings according to the ranking in that scoring.
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#51 User is offline   jtfanclub 

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Posted 2007-May-04, 18:42

Out of curiousity, what does it do to the odds if you use matching rather than scoring to even it out?

For example, rather than using the usual 'tree' structure, what happens if you use highest SOS vs. lowest, with equal number of points (ie., high vs. high) as the tiebreaker? While this may seem counterintuitive, not having the best players play each other may in fact make for a more 'fair' tournament.
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