BAM strategy?

[jillybean]

I am hoping to play in the Women's Bam Teams at the next nationals. Yeah, I know we are likely to be annihilated in the first round but I think it would be a good experience.

 

I understand the scoring is simply Win=2, draw=1, lose=0 but I don't know what strategies should be used. Typical IMP/MP strategies don't seem to be entirely applicable, so what is?

[TylerE]

Play it like MP. Overtricks matter. Going plus is better than going minus. *magnitude* doesn't matter. You can afford to be a bit riskier since like MP, at worse you take a bottom and move on.

[pooltuna]

I am hoping to play in the Women's Bam Teams at the next nationals. Yeah, I know we are likely to be annihilated in the first round but I think it would be a good experience.

 

I understand the scoring is simply Win=2, draw=1, lose=0 but I don't know what strategies should be used. Typical IMP/MP strategies don't seem to be entirely applicable, so what is?

 

 

I have heard this referred to as "super matchpoints" since making an overtrick is the difference between winning and losing the board.

[Phil]

Play it like MP. Overtricks matter. Going plus is better than going minus. *magnitude* doesn't matter. You can afford to be a bit riskier since like MP, at worse you take a bottom and move on.

 

Just don't lose the board at your table by trying to be a genius since your teammates are more reliable than a typical matchpoint field. Totally disagree that its "only a board". Its losing to MP strategy to take full board risks, and its bad BAM strategy too.

 

You need to protect more aggressively though. +200 is good at MPs but its great at BAM.

 

That being said, if you think you need some positive swings because you think you won't qualify otherwise, go ahead and step out a little.

[MickyB]

Yeah it's basically MP, except there are only two tables and you'll hopefully have a reasonable idea how your teammates will play.

[jjbrr]

JB don't worry too much about strategy. Play the best bridge you can play, and you'll do great.

[Rossoneri]

JB don't worry too much about strategy. Play the best bridge you can play, and you'll do great.

 

I agree, on most boards, it doesn't really make much of a difference.

[paulg]

Some of my friends teamed up to play the Mixed BAM in Toronto. There was a lot of trepidation as BAM is not a format that is ever played in Scotland and the only advice was "matchpoints, not imps". Afterwards they said that they really started to enjoy it around the middle of the second session and then, having just scraped through, had a lot of fun on the second day without threatening the first page of results sheet.

 

So just enjoy :)

[helene_t]

Yeah it's basically MP, except there are only two tables and you'll hopefully have a reasonable idea how your teammates will play.

This.

 

At BAM, you try to maximize your probability of doing better than your opps at the other table. At MP you do the same. It is true that there are many other tables and you want to maximize the sum of all the probabilities. But you typically won't have any idea about how specific tables will fare so from your point of view there is just a single probability distribution of raw scores that you try to beat. For example, suppose you are in 3NT and have the choice between two strategies:

Strategy A: 20% chance of -50 and 80% chance of 430

Strategy B: 100% chance of 400.

 

At BAM, if there is an overwhelming probability that the other table is also in 3NT (and receiving the same lead etc to the extent that it matters) you go for A. And also if the other table is almost certain to have 420. But if you think that the other table could just as easily be in 170 or 480 or w/e with 400, 420 and 430 not particularly likely, then go for the safe plan (B).

 

At MP your consideration should be exactly the same. Instead of the probability that thee other table gets between 399 and 431 you let your choice depend on the expected proportion of the other tables that get between 399 and 431. But that is, for decision purposes, exactly the same.

 

As Micky notes, however, it could be that you have a good idea about what happens at the other table. It does require you to know the style of your opponents at the other table, though. When bidding and declaring, you know your own cards and the question is if your opps at the other table bid the same way as you did. Whether your teammates bid and lead the same as your opps at your table is hard to tell before you have a picture of their hands. So I think knowledge of your teammates' style is useful mainly when defending. If you see the dummy and note that your teammate would have reached a different contract, you probably shouldn't go for an extra undoubled downtrick when they are green. Just set the contract.

 

More generally, BAM is 2-table matchpoints, and the size of the field doesn't matter for your choice of strategy. It does matter for other purposes (larger fields will yield more stable comparisons), though.

 

All this said, jjbr's point is by far the most important.

[Fluffy]

the big difference between bam and MPs is that 430 equals 420 at BAM, or at least that's what I though. (correct me if wrong)

[Phil]

the big difference between bam and MPs is that 430 equals 420 at BAM, or at least that's what I though. (correct me if wrong)

 

Nope

[Cyberyeti]

the big difference between bam and MPs is that 430 equals 420 at BAM, or at least that's what I though. (correct me if wrong)

Depends on the precise form of BAM being played. The nearest we get in the UK is a hybrid system where 4 board matches are scored out of 8 for BAM and out of 4 for aggregate/swing, here 430=420, but in pure BAM it can vary.

[ArtK78]

In BAM as played in the US, 430 beats 420.

 

There are some peculiar situations that arise in BAM that come up in no other form of scoring.

 

Suppose you are in 1NT, which is a normal contract. The opponents have gotten off to an incredibly poor defense and you are assured of making 180. Even 150 would be an almost certain win on the board, and you can't score less than 150 no matter how you play.

 

You notice that your opps are vul. Given that you are assured of winning the board if you score 150 or more, you should take some extra chances to try and score 210 on the off chance that your vulnerable teammates go for 200.

 

I read this in a book some years ago, and I don't remember the name of the author. But on this particular hand, the declarer risked his 180 and obtained 210, winning the board when his teammates did in fact go for 200.

[semeai]

In BAM as played in the US, 430 beats 420.

 

There are some peculiar situations that arise in BAM that come up in no other form of scoring.

 

Suppose you are in 1NT, which is a normal contract. The opponents have gotten off to an incredibly poor defense and you are assured of making 180. Even 150 would be an almost certain win on the board, and you can't score less than 150 no matter how you play.

 

You notice that your opps are vul. Given that you are assured of winning the board if you score 150 or more, you should take some extra chances to try and score 210 on the off chance that your vulnerable teammates go for 200.

 

I read this in a book some years ago, and I don't remember the name of the author. But on this particular hand, the declarer risked his 180 and obtained 210, winning the board when his teammates did in fact go for 200.

 

This should all apply at matchpoints too. See Helene's post for why they're equivalent.

 

The difference could come in if you know your teammates are less likely to defend terribly and allow the 150 or 180 or more likely to be active and go for 200 than the generic member of a matchpoint field.

 

Added: The above is just thinking in terms of EV. I suppose it's more worth your effort to care about this at BAM, since a 3% chance at a full board is more likely to matter for the event than 3% of a board. Other differences in the two formats may come in when it's right not to maximize EV for various reasons.

[jillybean]

Thanks all. I think having fun and playing the best we can will be our strategy. We won't know the style of our opponents, we are relatively inexperienced

partnerships and barely know the style of our team mates but regardless, I think it will be fun and a great experience.

[ArtK78]

This should all apply at matchpoints too. See Helene's post for why they're equivalent.

 

The difference could come in if you know your teammates are less likely to defend terribly and allow the 150 or 180 or more likely to be active and go for 200 than the generic member of a matchpoint field.

 

Added: The above is just thinking in terms of EV. I suppose it's more worth your effort to care about this at BAM, since a 3% chance at a full board is more likely to matter for the event than 3% of a board. Other differences in the two formats may come in when it's right not to maximize EV for various reasons.

This hand actually shows the difference between matchpoints and BAM.

 

In a matchpoint field, you can bet that 180 will outscore 150. In fact, you can be reasonably certain that the difference between 150 and 180 will be significantly more than the difference between 180 and 210. The 200 number is likely to be an extreme result, and may not occur. So attempting to score 210 by risking your 180 may gain you zero or one matchpoint if you are successful, at the risk of several.

 

[180 also outscores 160, which is a possible number in a matchpoint field, but you can probably be safe in ignoring it at BAM. Whether 170 is a possible number is a matter of judgment, but it did not come into play on the board that I was discussing above.]

 

But at BAM, if you can know with reasonable certainty that the difference between 150 and 180 is zero, it is worth it to try to protect your teammates against an unlikely but possible unfortunate 200 number.

[helene_t]

The above is just thinking in terms of EV. I suppose it's more worth your effort to care about this at BAM, since a 3% chance at a full board is more likely to matter for the event than 3% of a board. Other differences in the two formats may come in when it's right not to maximize EV for various reasons.

In general I think maximizing EV is fine regardless of what your aim is.

 

Obviously you should go for high-variance strategies if you are unlikely to reach your aim (in a BAM match that would mean: when you are underdog and/or have to catch up towards the end of the match) and low-variance when you are likely to reach your aim. At BAM, a low-variance strategy is one that gives a good chance of a draw while at MP, a low-variance could also for example be -50 or +50 when you expect that most of the field would be -110 or +110 or such. This also means that high-variance vs low-variance may be slightly more relevant at MP than at BAM. At the club duplicate we have barometer and when we are first in the field with two boards to go I would tend not to do risky things like doubling them when I estimate that an undoubled downtrick would already give us something close to 50%, although that consideration is obviously more relevant at XIMPs than at MP.

 

But I think this is a very subtle difference, hardly worth worrying about.

[semeai]

This hand actually shows the difference between matchpoints and BAM.

 

In a matchpoint field, you can bet that 180 will outscore 150. In fact, you can be reasonably certain that the difference between 150 and 180 will be significantly more than the difference between 180 and 210. The 200 number is likely to be an extreme result, and may not occur. So attempting to score 210 by risking your 180 may gain you zero or one matchpoint, at the risk of several.

 

[180 also outscores 160, which is a possible number in a matchpoint field, but you can probably be safe in ignoring it at BAM. Whether 170 is a possible number is a matter of judgment, but it did not come into play on the board that I was discussing above.]

 

But at BAM, if you can know with reasonable certainty that the difference between 150 and 180 is zero, it is worth it to try to protect your teammates against an unlikely but possible unfortunate 200 number.

 

I'm happy if you're saying all this because of the difference between your teammates and the generic member of a matchpoint field.

 

If not, I disagree. If we suppose x% of the field will get 150, y% will get 180, z% will get 200, and w% will get 210 (and ignore the rest, as they're irrelevant; for simplicity let's suppose no 160/170 etc), and we know nothing about your teammates, we should also suppose, as Helene said, that your teammates have a probability (in percentage form for clarity) of x% of getting 150, y% of getting 180, z% of getting 200, w% of getting 210.

 

If you're considering trading 180 for probability p of 210 and (1-p) of 150, the difference in your EV is the same at either matchpoints or BAM. In both cases it's p*(w/2 + z + y/2) - (1-p)*(y/2 + x/2).

 

Added: If you're worried the matchpoint field isn't large enough for certain results to appear, more of the same sort of analysis will again show the EV is the same (show BAM and your matchpoint event are both the same in terms of EV as some idealized really big matchpoint event).

[1eyedjack]

Some years ago I played in the Pachabo here in England. They may have changed the format since, but as I recall it was something of a hybrid scoring system. There were (I think) 6 VPs at stake on a hand, of which 2 were awarded for simply winning the hand (as with simple BAM) and the remaining 4 were issued based on IMP difference. I felt that this format rewarded careful and skilful bridge, while at the same time providing a bit more incentive to stretch for difficult overtricks at the expense of safety, without obliterating the safety aspect.

[helene_t]

Jack: that's called Patton. I agree it's a great form of scoring. There is a yearly Patton event at 't Onstein bridgeboerderij in Voorden, NL.

[Cyberyeti]

Jack: that's called Patton. I agree it's a great form of scoring. There is a yearly Patton event at 't Onstein bridgeboerderij in Voorden, NL.

I like it too, is what I was describing in my earlier post.

 

If you want to bring Max Bavin out in a cold sweat, ask him about the time they tried to use it in the easter Guardian about 30 years ago with no computers on the tables and a load of LoLs trying to calculate aggregate/swing.

[gnasher]

the big difference between bam and MPs is that 430 equals 420 at BAM, or at least that's what I though. (correct me if wrong)

 

That's common in parts of Europe, but not in North America. There's a thread about it here:

 

http://www.bridgebase.com/forums/topic/31514-board-a-match/

[han]

Vorden. :)

[JLOGIC]

Just pretend like it's MP. If you never try to predict the other room, you will probably be ahead of most other people who vary their bids/plays by trying to predict the room. It's like how most card counters in blackjack make errors so casinos don't care.

 

More on how BAM and MP are very similar: Say you have a normal/good average plus board that you would expect 75 % on in MP. In BAM, you might have a 50 % chance to win the board, and 50 % to tie it. It is the same thing.

[barmar]

I'm happy if you're saying all this because of the difference between your teammates and the generic member of a matchpoint field.

 

If not, I disagree. If we suppose x% of the field will get 150, y% will get 180, z% will get 200, and w% will get 210 (and ignore the rest, as they're irrelevant; for simplicity let's suppose no 160/170 etc), and we know nothing about your teammates, we should also suppose, as Helene said, that your teammates have a probability (in percentage form for clarity) of x% of getting 150, y% of getting 180, z% of getting 200, w% of getting 210.

 

If you're considering trading 180 for probability p of 210 and (1-p) of 150, the difference in your EV is the same at either matchpoints or BAM. In both cases it's p*(w/2 + z + y/2) - (1-p)*(y/2 + x/2).

 

Added: If you're worried the matchpoint field isn't large enough for certain results to appear, more of the same sort of analysis will again show the EV is the same (show BAM and your matchpoint event are both the same in terms of EV as some idealized really big matchpoint event).

What you're basically saying is that a strategy that averages 60% on all the boards in MP is the same as one that wins 60% of the boards in BAM, but this assumes that your teammates are equivalent to a matchpoint field. If you think your teammates are better than the field, you can assume that they're not giving away the gifts you're receiving. Then when you get a gift, you now have the opportunity to take a risk that's likely to at worst give it back (only risking half a board) but which might turn a loss into a win if something weird happened at the other table.

 

On the other hand, if you think your teammates are worse than the field, you should play carefully -- you can't afford to give gifts at both tables.