BAM play problem

[Guest Jlall]

I liked AK here. Slightly surprised it proves a BAM winner on spade contracts at both tables

then why did you like AK? You thought it would be a winner vs 3N and not vs spades and that the opponents would be in 3N? It is really a big view to take a line you think is anti percentage because you are in the best game and its a 4-4 fit.

 

- did we actually prove that?

 

I proved it if you agree with some of my assumptions. I effectively set the probability of a defensive error at 0, set the probability of the ace being onside and the queen being onside (in diamonds) as equal, and set the probability of the SQ being in the same hand as equal. I also made the likelihood of me guessing diamonds if LHO has Qxx of spades and gets ended 50/50. If you think that the queen being onside is significantly more likely than the ace in diamonds being onside then that may tip the scales towards hooking the spade. If you think you will be able to guess the diamonds 60 % of the time that will make playing the AK of spades more attractive.

 

The math part of bridge is typically not hard, it's find and accurately take inferences and adjust the probabilities that is what makes the top player better than a good player. This is subjective and hard to include into calculations.

 

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We are not claiming we calculated this at the table are we?

 

Obviously you cant calculate everything precisely, but you can see if you look deeply at it that you are going to frequently make 11 tricks by playing AK when you otherwise would have made 10, but you decrease chances of making 12. It also looks (to me) like you are gaining more than you are losing by playing the AK of spades. That is how I thought about it at the table.

[sathyab]

Obviously you cant calculate everything precisely, but you can see if you look deeply at it that you are going to frequently make 11 tricks by playing AK when you otherwise would have made 10, but you decrease chances of making 12. It also looks (to me) like you are gaining more  than you are losing by playing the AK of spades. That is how I thought about it at the table.

In the 1.5 or two minutes that you have available to play to trick 1, you were able to figure out that playing the AK of spades increases your chances of making 11 tricks but reduces the chances of making 12 tricks ? Really ?

 

It's far from clear even with all your analysis why or how much one line is superior to the other. Numbers like 47% for one line and 44% for the other don't pop up at the table for most of us and even if they did that could hardly be the basis for doing some unorthodox like rejecting a routine finesse in trumps.

 

It'd be nice if we had play records available so we could at least see how the good players, of whom there'd be so many in a BAM event, played it even if we wouldn't know why they did what they did.

[Guest Jlall]

Obviously you cant calculate everything precisely, but you can see if you look deeply at it that you are going to frequently make 11 tricks by playing AK when you otherwise would have made 10, but you decrease chances of making 12. It also looks (to me) like you are gaining more  than you are losing by playing the AK of spades. That is how I thought about it at the table.

In the 1.5 or two minutes that you have available to play to trick 1, you were able to figure out that playing the AK of spades increases your chances of making 11 tricks but reduces the chances of making 12 tricks ? Really ?

Yes? Isn't this obvious? You only make 12 tricks when its Qx of spades off and the DA on by playing AK...by finessing you make 12 tricks when its Qxx on and DA on. Both lines make 12 when its Qx on and DA on. Qxx is obviously more likely than Qx.

 

For 11 tricks playing AK obviously increases your chances since you can just endplay RHO if he has Qxx.

 

That took maybe about 5 seconds not 2 minutes. I'm not sure what people who don't figure that out spend time thinking about if they don't think about even that. Only after you figure out the percentage line (as in the line most likely to succeed in your goal with no other information) should you even begin to start thinking about things that may alter the percentages like the lead, the other table, the failure by the opponents to bid, etc.

 

Numbers like 47% for one line and 44% for the other don't pop up at the table for most of us and even if they did that could hardly be the basis for doing some unorthodox like rejecting a routine finesse in trumps.

 

You don't need to come up with exact percentages to figure out whether one line is better than another. You don't even need to come up with any percentages. You can just come up with cases where one line wins against another vs one line losing against another and figure out which is more likely most of hte time. I don't understand how this can not be the basis for making a certain play, making the play most likely to win should be the basis of ALL plays. All I can do is rofl at calling this a routine finesse, just because a finesse is available does not make it routine. Saying you can't fail to take that line because of "numbers" is really funny too.

 

It'd be nice if we had play records available so we could at least see how the good players, of whom there'd be so many in a BAM event, played it even if we wouldn't know why they did what they did.

 

Results:

 

Obviously I am not a good player but I will tell you what happened. I played AK of spades and later played LHO for the DQ in order to try and tie the board if they hooked at the other table. 10 tricks. At the other table they opened a strong club and got intervention from a bad hand on their right showing the reds so obviously they finessed the spade. Fredrik Nystrom played identically to me. Marty Fleisher took 2 finesses. My partner said he agreed with my line.

[Stephen Tu]

Well, I don't think one can do the long form of computation like Justin did in a normal amount of time, but I think one can estimate that, roughly,

(doubleton Q off + 0.5 (tripleton Q off)) > (0.75 (tripleton Q on))

if one is going to make no major assumptions about the diamond honors because

of the lead. (This is inaccurate because of vacant spaces, but one doesn't have time to calculate to the last percent without Rain Man abilities)

 

Basically AK wins if you drop the Q or can gain by endplaying RHO. It loses to the hook with tripleton onside + no endplay recovering trick (LHO Q of d alone, which makes you break even). I haven't thought too much about the 4-1 cases.

(I think in Justin's calc he didn't break out the case where LHO has SQxx + DAQ, so his numbers are likely off)

 

Comparing vs. 3nt is difficult, who knows whether diamond or heart is the natural lead ...

[Guest Jlall]

(I think in Justin's calc he didn't break out the case where LHO has SQxx + DAQ, so his numbers are likely off)

yes you are correct, it took me forever to write that post and I'm at work and overlooked this. Also 4-1s are a little complicated.

 

And yes comparing vs 3N is ridiculously complicated.

[whereagles]

Why all this fuss? Clearly ♠AK is a good line, as is finessing twice.

[sathyab]

[

You don't need to come up with exact percentages to figure out whether one line is better than another. You don't even need to come up with any percentages. You can just come up with cases where one line wins against another vs one line losing against another and figure out which is more likely most of hte time. I don't understand how this can not be the basis for making a certain play, making the play most likely to win should be the basis of ALL plays. All I can do is rofl at calling this a routine finesse, just because a finesse is available does not make it routine. Saying you can't fail  to take that line because of "numbers" is really funny too.

 

It'd be nice if we had play records available so we could at least see how the good players, of whom there'd be so many in a BAM event, played it even if we wouldn't know why they did what they did.

 

Results:

 

Obviously I am not a good player but I will tell you what happened. I played AK of spades and later played LHO for the DQ in order to try and tie the board if they hooked at the other table. 10 tricks. At the other table they opened a strong club and got intervention from a bad hand on their right showing the reds so obviously they finessed the spade. Fredrik Nystrom played identically to me. Marty Fleisher took 2 finesses. My partner said he agreed with my line.

Even if you can figure out which line of play offers a better chance for 11 tricks and which one for 12 tricks, to reject the line that offers 12 tricks in favor the 11 trick lineyou must have a strong reason. So far I haven't seen any compelling argument that says the 11 trick line was more likely than the 12 trick line.

 

Sorry if you thought I was implying that you were not a good player, I certainly didn't intend to. No matter how good a player one is, the Fall Nationals is a veritable collection of who-is-who in the world of bridge. When my partner and I found ourselves sixteenth in the qualifying list for the Blue Ribbon Pairs finals, I was telling a director from the Bay Area that our names were the only ones that I couldn't recognize in that illustrious list :) It was in that vein that I used the phrase "good players". My apologies again if it came across differently.

[Stephen Tu]

Even if you can figure out which line of play offers a better chance for 11 tricks and which one for 12 tricks, to reject the line that offers 12 tricks in favor the 11 trick lineyou must have a strong reason. So far I haven't seen any compelling argument that says the 11 trick line was more likely than the 12 trick line.

 

It's not efficient at all to think in terms of total # of tricks taken. If comparing just two lines just count cases where one takes "more" tricks, don't worry about how many total you are taking.

 

AK line takes more tricks when the Q is doubleton offside. This is 12 vs. 11 or 11 vs. 10 depending where the DA is.

 

AK line also takes more tricks when the Q is trebleton offside + DA offside. This is 11 vs. 10.

 

finesse line takes more tricks when Q is trebleton onside, & LHO doesn't have the DQ only. Some of these are 12 vs. 11, some 12 vs. 10, some 11 vs. 10. But # of tricks the other line beats you by doesn't matter in BAM assuming same contract.

 

Just count total percentages of winning/losing cases, waste of time to calculate exactly when it's 12 vs. 11 or 11 vs. 10 or 12 vs. 10.

 

If you count just these cases, one gets an advantage of ~8% or so for the AK line. Now, perhaps there are some 4-1 split cases I am overlooking, & perhaps there are lead inferences about the DA, but don't know if enough to cancel this out.

[Halo]

The AK line does not always gain against Qx offside since the hearts are eliminated.

 

However, calculating correctly (my version of properly!) and taking account of changing odds there is an irreducible 1% or slightly more advantage to cashing AK - madeup of less than half the cases where East has doubleton or trebleton Q of spades, versus 75% or so of the cases where West has Qxx.

[Stephen Tu]

The AK line does not always gain against Qx offside since the hearts are eliminated.

 

It will gain on almost all of these; RHO will have club exit cards most of the time. If you play clubs to increase the endplay possibilities here you run into alternate risk of club ruffs. How do you get "less than half" of the offside doubleton Q possibility winning?

 

The main thing my calcs omitted was a few percent when spades 4-1 onside, & defense can tap dummy in diamonds or run diamonds after trumps drawn. Still prob 5% edge for SAK.

[Halo]

Expressed myself badly.

 

I started by thinking that the finesse was best if both sides played in spades and AK if 3NT was in the frame. I was wrong. Even if we could eliminate clubs and hearts before finessing, it would actually still be better (by a small amount) to just cash AK of spades.