MP vs IMPs

[nige1]

Stating the obvious:

 

At MPs, each board has equal weight, so most boards are important. Your action often requires calculations that depend on your guess at happenings at other tables. Rarely, can you relax. In general, a good MP player bids and plays as well as he can. Towards the end of a tournament that he thinks he's winning, he may "go with the field", to try to maintain his advantage. Otherwise, he "goes with the room" only when he judges that the popular action is likely to be best.

 

At imps, boards differ wildly in importance. Usually, grand-slam >> small-slam >> game >> part-score >> extra under-trick >> extra over-trick. Hence, at imps, part of the skill is to avoid wasting adrenalin on insignificant boards, so that you focus attention on boards that you judge might be decisive. Thus, for example, in a long match, good players claim when they might play on in the hope of an unlikely over-trick.

 

If you compete against the same number of equally skilled players in a teams-of-6/teams-of-4/ pairs/individual event, your chance of winning is in the ratio 6:4:2:1.

 

In most Bridge events, there is a further multiplier effect. Good players tend to gang-up. It's hardly surprising that a team consisting of the best 4 or 6 available players tends to dominate teams of lesser players. This effect is also noticeable (to a lesser extent) in pairs. Individual events test individual skills. Lacking the multiplier effect, however, individual results are less predictable.

 

If you are a professional, I guess that teams >> pairs and individuals come nowhere.

[helene_t]

I could also have made a comparison of chess versus sumo wrestling. Of course you could say that such a comparison is silly since different skills are required. However, it is still a meaningful question to ask how much luck in involved in a given chess tourney compared to a given sumo tourney. It would not be meaningful to ask whether say 60 minutues of head-to-head chess in general involves more luck than 60 minutes of head to head sumo wrestling because it will depend of the strength difference between the contestants, which can't be compared.

 

As for MP vs IMPs, we can compare the two things is we assume that the average total points that pair A will win over pair B per board is a universal measure of strength difference which can be applied to both IMPs and MP. In other words, I have assumed that there is such a thing as an objective strength difference between two pairs, and one can ask which tournament format, and which form of scoring, captures that strength difference best.

 

It may well be that for a particular pair of pairs, A>B for matchpoints while B>A for IMPs. That doesn't matter. The only crucial assumption is that the strength difference can be expressed on a common scale.

 

Suppose it is so that the total points swings are larger in IMPs than in MPs (for example because people bid more grands) while there are also more washes (for example because there are fewer contested auctions). In that case the total points would have a different distribution and the assumption become a bit dubious.

 

But if we had real data this might not be a problem. Suppose we have two pair we frequently meet each other, sometimes in XIMP tourneys and sometimes in MP tourneys. One of the two pairs will appear to be the stronger of the two in the sence that regardless of scoring, they tend to win if the tourneys are long enough. If the win probability converges faster for (say) MP than for XIMP, it would suggest that MP involves less luck, at least w.r.t. the kind of tourneys these two pair play in. Of course it could be that the stronger pair is especially better at MP. But if the pattern repeats itself when considering other pairs then it is a good case that (say) MP is less luck dependent.

 

Of course one could argue that it is just because the MP tourneys they meet each other in have a more homogenous field or a more balanced movement etc but it may be possible to take such factors into account.

[jogs]

Compare this to sports. mps is the regular season. It is about beating the pigeons. IMPs(knockouts) is the playoffs. It is the best vs the best. The winner is declared the champion for the year.

[nige1]

As for MP vs IMPs, we can compare the two things is we assume that the average total points that pair A will win over pair B per board is a universal measure of strength difference which can be applied to both IMPs and MP. In other words, I have assumed that there is such a thing as an objective strength difference between two pairs, and one can ask which tournament format, and which form of scoring, captures that strength difference best.

I think that both forms of competition require similar skills but helene-T's allusion to total-point scoring highlights an important difference.

 

Total-points >> imps >> MPs when judging the significance of individual boards in deciding the overall result.

 

Some time ago, at an Edinburgh club, total-points was the normal pairs-scoring method. When doing uncharacteristically badly, towards the end of a tournament, regular winners sometimes rescued their fortunes by doubling wildly or bidding an odds-against slam. A single large score would sometimes be decisive.

 

Nowadays, In Scotland, team-of-eight leagues are scored total-points. The match-result can hinge on a single board e.g. where one pair bid a grand-slam. For a different match-result, you would have to change several other board-results.

[Cthulhu D]

It is your arguments, which look flawed to me. .

Contract Bridge is in itself a game where certain contracts are rewarded and others not, "because the scoring system does not reward it". A tautology.

Unforced by opponents 5♥,5♠,4♣,4♦,3♥,3♠,2NT are all examples of such unrewarding contracts.

Does this make the game flawed?

On the contrary.

 

These are just prejudices against some form of the game (in this case MP).

 

Rainer Herrmann

 

It seems fairly clear to me that the decision to bid past 4H and try for slam is a proactive use of judgement. I think that is very different than refusing to use judgement when opening 1NT?

[nige1]

Compare this to sports. mps is the regular season. It is about beating the pigeons. IMPs(knockouts) is the playoffs. It is the best vs the best. The winner is declared the champion for the year.

Jogs is correct that If you're poor in bridge-skills but rich in money and you want to become a champion, then you have a better chance at IMPed teams than at BAM or at MP pairs.

[jogs]

Change the rules of knockouts to 8 16 board segments. First team to win 4 1/2 segments wins the match. Would put playing sponsors who can't play at a disadvantage.

[Vampyr]

IMPs and MPs are interesting and valid forms of scoring. The premise in the other thread was that IMP pairs is neither.

[rhm]

It seems fairly clear to me that the decision to bid past 4H and try for slam is a proactive use of judgement. I think that is very different than refusing to use judgement when opening 1NT?

I play a lot of MP and IMPs and I play long enough being exposed to money Bridge as well.

I have never found I should not use judgement when playing MP when to open 1NT or on any other Bridge decision.

The considerations are sometimes different at MP and I understand that some people have difficulties adjusting to different forms of the game, but it is plain wrong (in fact silly) to claim you will get good results by not using judgement at MP.

What people usually mean, who claim something like this, is that they are unable to cope with these different considerations and apply judgement suitable for MP.

 

Rainer Herrmann

[Cthulhu D]

I play a lot of MP and IMPs and I play long enough being exposed to money Bridge as well.

I have never found I should not use judgement when playing MP when to open 1NT or on any other Bridge decision.

The considerations are sometimes different at MP and I understand that some people have difficulties adjusting to different forms of the game, but it is plain wrong (in fact silly) to claim you will get good results by not using judgement at MP.

What people usually mean, who claim something like this, is that they are unable to cope with these different considerations and apply judgement suitable for MP.

 

Rainer Herrmann

 

I definitely play a lot better at IMPs, and that may be biasing me. It is reasonable to assume this is because the system I play with a regular partner (which is hugely anti-field for MP games, we are typically the only pair playing 14-16 NT, the only pair playing assumed fit openers, the only pair without a 2H weak 2 opening, the only pair with 1C = clubs or balanced, etc, etc you get the idea), is more effective at swiss pairs and teams against opponents of my (intermediate at best) skill level. But I'm not saying you'll get good results by not using judgement at MPs, that is obviously dumb and a total straw man of my argument. I'm saying that match-points occasionally creates an incentive for you to make decisions that, based on your judgement, you think are inferior.

 

Here is a little thing by a better player than me discussing illustrating issue: http://www.jeff-goldsmith.org/html/hardtoplan.html (paragraph one)

 

Of course, this is a minor detail and is obviously swamped by the other decisions that you have to make (e.g. see, the next 4 paragraphs of the column!) but it's a very interesting feature of that form of the game.

[nige1]

I'm saying that match-points occasionally creates an incentive for you to make decisions that, based on your judgement, you think are inferior. Here is a little thing by a better player than me discussing illustrating issue:

http://www.jeff-gold...hardtoplan.html (paragraph one)

Cthulhu D's quotation doesn't seem to support his contention...

At IMPs, one usually knows the target number of tricks one wants to take; it is often worth taking big chances to make a contract. At matchpoints, however, sometimes one's trick goal is less clear.

[Cthulhu D]

Sorry, O meant paragraph one of his description of the hand, which is as follows

 

I have found that downgrading 15-counts, even the really crappy one here, is losing matchpoints. Most of the field is going to open 1NT; to be the one pair who doesn't is to bet a full board on that one judgment. Since at best such a judgment can only provide a tiny edge, such a call is tantamount to rolling dice for the board. Oddly, it's not usually the constructive nature of the 1NT opening which is key in cases like this, but the preemptive effect.

[nige1]

I have found that downgrading 15-counts, even the really crappy one here, is losing matchpoints. Most of the field is going to open 1NT; to be the one pair who doesn't is to bet a full board on that one judgment. Since at best such a judgment can only provide a tiny edge, such a call is tantamount to rolling dice for the board. Oddly, it's not usually the constructive nature of the 1NT opening which is key in cases like this, but the preemptive effect.

On the featured deal, Jeff Goldsmith demonstrates bridge skill and good MP judgement. Crowhurst also recommends the 1N opening at MPs. When non-vulnerable, the first side to bid 1N often makes an MP profit, whether the contract makes 5, 6, 7, or more tricks.

[awm]

Since the decision of whether to open 1nt is pretty likely to effect whether game is reached, it seems like Jeff Goldsmith's point could also be applied to IMPs?

[Cthulhu D]

In other articles he opens broadly comparable hands 1m so given he specifically referenced Matchpoints I am going to assume he specifically makes this decision at MPs.

 

@nige1: yes, that is precisely my point. That is a weird/intresting artifact of the scoring system. He's overriding his judgement to open 1suit because of the way to the scoring works.

[jdeegan]

Nobody can properly analyze 9000 bridge hands.

 

Madam, you are a fakir and a fraud. You are an idiot turned loose with a computer and a first year grad student's knowledge of statistics.

 

You present a double dummy playing analysis based on a potentially very biased sample.

[nige1]

@nige1: yes, that is precisely my point. That is a weird/interesting artifact of the scoring system. He's overriding his judgement to open 1suit because of the way to the scoring works.

It depends on where you're coming from. You could equally argue that he is using his MP judgement to open 1N. Or you might just conclude that he adapts his strategy to the relevant scoring method and his tactics to the current competitive context.

[nige1]

Nobody can properly analyze 9000 bridge hands. Madam, you are a fakir and a fraud. You are an idiot turned loose with a computer and a first year grad student's knowledge of statistics. You present a double dummy playing analysis based on a potentially very biased sample.

I find this topic interesting. Helene_t (who is unlikely to be a Fakir) went to some trouble to investigate it. We can disagree with her methods or conclusions but ad hominem attack sidetracks discussion and wastes our time. Better to present relevant data and constructive argument of our own.

[suokko]

Nobody can properly analyze 9000 bridge hands.

 

Madam, you are a fakir and a fraud. You are an idiot turned loose with a computer and a first year grad student's knowledge of statistics.

 

You present a double dummy playing analysis based on a potentially very biased sample.

 

I can do a written analyze at 20 boards per hour speed. If that was my day job it would take only 3 months to analyze 9000 bridge hands.

 

But actual arguments for practical randomness in IMP vs MP games.

 

Normal winner score in MP is around 57-65% in competitions where skill level difference aren't big. If a tournament is about 40 boards then single board top-bottom difference is 2.5% in end results. But in practical play my opponents cannot score more than 2/3 of top with a good play. That translates to about 1.6% at stage each board which is 1/9 of score difference between winner and average. But even a good play can be often countered with a less important decision that still score a few points back to side that didn't have the more important decision to make.

 

At similar IMP competition winner score is +1.5-2.5 IMP per board per comparison. But a single vulnerable game swing is 10-14 IMPs per comparison. That translates to about 0.25-0.35 IMPs per board and those decision are pretty common with only one side having decisions that affect the make or not make situation. So even a normal game swing has a higher magnitude in IMPs than extreme maximum MP games offer. But if we factor in some extreme IMP swings with small slam their effect can be even twice the effect that games have. That makes IMP scoring more volatile because smaller number of important decision provide relatively higher magnitude changes to the results.

[Cthulhu D]

I can do a written analyze at 20 boards per hour speed. If that was my day job it would take only 3 months to analyze 9000 bridge hands.

 

But actual arguments for practical randomness in IMP vs MP games.

 

Normal winner score in MP is around 57-65% in competitions where skill level difference aren't big. If a tournament is about 40 boards then single board top-bottom difference is 2.5% in end results. But in practical play my opponents cannot score more than 2/3 of top with a good play. That translates to about 1.6% at stage each board which is 1/9 of score difference between winner and average. But even a good play can be often countered with a less important decision that still score a few points back to side that didn't have the more important decision to make.

 

At similar IMP competition winner score is +1.5-2.5 IMP per board per comparison. But a single vulnerable game swing is 10-14 IMPs per comparison. That translates to about 0.25-0.35 IMPs per board and those decision are pretty common with only one side having decisions that affect the make or not make situation. So even a normal game swing has a higher magnitude in IMPs than extreme maximum MP games offer. But if we factor in some extreme IMP swings with small slam their effect can be even twice the effect that games have. That makes IMP scoring more volatile because smaller number of important decision provide relatively higher magnitude changes to the results.

 

I agree re: Variance. Jeff has done some analysis of this here: http://www.jeff-goldsmith.org/bridge/study

[PhilKing]

I find this topic interesting. Helen_t (who is unlikely to be a Fakir) went to some trouble to investigate it. We can disagree with her methods or conclusions but ad hominem attack sidetracks discussion and wastes our time. Better to present relevant data and constructive argument of our own.

 

One should only be able to start a thread like if one has a phd in statistics.

 

Oh, wait ... B-)

[cherdano]

So within a few hours, Helene (who knows more statistics than anyone on this forum), gets

- called "an idiot turned loose with a computer and a first year grad student's knowledge of statistics", and

- gets mansplained (in another thread) the most basic thing one could explain about standard variance.

 

I am sure one could explain this without referring to sexism, but I doubt it would lead to the easiest explanation.

[kuhchung]

So within a few hours, Helene (who knows more statistics than anyone on this forum), gets

- called "an idiot turned loose with a computer and a first year grad student's knowledge of statistics", and

- gets mansplained (in another thread) the most basic thing one could explain about standard variance.

 

I am sure one could explain this without referring to sexism, but I doubt it would lead to the easiest explanation.

 

ignorance and internet behavior

[PhilKing]

So within a few hours, Helene (who knows more statistics than anyone on this forum), gets

- called "an idiot turned loose with a computer and a first year grad student's knowledge of statistics", and

- gets mansplained (in another thread) the most basic thing one could explain about standard variance.

 

I am sure one could explain this without referring to sexism, but I doubt it would lead to the easiest explanation.

 

By an astounding coincidence, they are the two people on my ignore list - I only saw the posts because their idiocy was quoted for posterity ...

[gwnn]

I'm not sure how "first year grad student's" knowledge of statistics is supposed to be some kind of insult (it kind of is to Helene but I am talking in abstract). That would be probably something in the top percentile of even reasonably educated people and definitely above everyone on TV.