playing 3Nt rather than 4M in 8cards fit.

[rhm]

Because a double-dummy simulation represents double-dummy play, and real-life results reflect real-life play. When designing bidding methods, I'm interested in the results that I would get in real life, not the results that I would get if everyone could see all the cards.

 

Here are some reasons why double-dummy analysis might, in this situation, provide misleading results:

- In four of the major we may have time to try several different finesses, whereas in 3NT we may have to guess which finesse to take. DD analysis will assume that we would get the guess right.

- In four of the major we may be able to avoid a guess by an elimination. DD analysis assumes that we would get the guess right in 3NT.

- In 3NT, with the declaring side 3-3 or 3-2 in all the side-suits, it will quite often be right to make a short-suit lead. DD analysis assumes that the defenders would do this. Whether they would do at the table depends on the auction: on an unrevealing auction like 1NT-2♥;2♠-3NT it will be hard for the opening leader to do this; on an auction where the declaring side announce a fit, discover that opener is 4333, and then settle in 3NT, it will be easier.

- Against four of the major real-life defenders may choose to make an attacking lead, whereas double-dummy defenders know that there are no discards to be had, so no need to attack.

 

I don't know how much these and other factors affect the relationship between double-dummy and single-dummy results, but I'm certain that it's wrong to extrapolate from double-dummy to single-dummy without considering them.

This has been raised often, but double dummy analysis is apparently still poorly understood.

Yes double dummy analysis is not real Bridge, because real Bridge is about single dummy analysis and human errors.

 

However, what has been known for a long time is that over a number of deals the result of double dummy analysis is close to single dummy analysis.

Double dummy results are a very good proxy for single dummy results.

This happens because the differences you mention cancel each other out. Neither defense nor declarer play is double dummy.

 

What difference remains can be quantified.

Low notrump contracts slightly favor declarer single dummy, while slam contracts slightly favor the defense.

For 3NT declarer's advantage is 0.2 tricks, for 4M it is zero.

Extrapolating from a small sample of real life plays is problematic, because

 

a) a small sample may not be representative.

b) you have little control what extraneous information there was available at the time of the decision at the table and you will not get these specific deals in your lifetime.

 

Rainer Herrmann

[gnasher]

However, what has been known for a long time is that over a number of deals the result of double dummy analysis is close to single dummy analysis.

Double dummy results are a very good proxy for single dummy results.

This happens because the differences you mention cancel each other out. Neither defense nor declarer play is double dummy.

 

What difference remains can be quantified.

Low notrump contracts slightly favor declarer single dummy, while slam contracts slightly favor the defense.

For 3NT declarer's advantage is 0.2 tricks, for 4M it is zero.

 

I have given you reasons why double-dummy results may not accurately model single-dummy results in this particular situation, that is specifically when we hold a 5=3=3=2 opposite a 4=3=3=3. Do you have evidence that for this specific situation these factors cancel out? If so, I think you should share this evidence.

[gnasher]

This has been raised often, but double dummy analysis is apparently still poorly understood.

You seem to be confusing scepticism with a lack of understanding.

 

I'm not sure what leads you to believe that I don't understand double-dummy analysis. I understand it very well. In this instance I simply don't accept your conclusions, given the evidence that you have so far provided.

Edited February 10, 2013 by gnasher

[rhm]

I have given you reasons why double-dummy results may not accurately model single-dummy results in this particular situation, that is specifically when we hold a 5=3=3=2 opposite a 4=3=3=3. Do you have evidence that for this specific situation these factors cancel out? If so, I think you should share this evidence.

The reason is if double dummy works as a good proxy for the expected result single dummy in general, there is no Bridge (or statistical) reason why the results should somehow be different when making some specific Bridge assumptions about distribution and HCP, but which are otherwise not related to the play of the hand itself.

What matters is only whether the number of deals in the simulation is high enough to give an approximation about the actual result for the total number of possible deals where this scenario can exist.

 

You seem to be confusing scepticism with a lack of understanding.

 

I'm not sure what leads you to believe that I don't understand double-dummy analysis. I understand it very well. In this instance I simply don't accept your conclusions, given the evidence that you have so far provided.

I am sure you know what double dummy analysis is bridge wise. The argument you use is Bridge related when the main argument is related to statistics, not Bridge.

You claim double dummy analysis is not real Bridge. Therefore you have little confidence in double dummy simulations.

But nobody claims this to be the case.

The claim is only that the result of double dummy analysis over many boards approaches single dummy real life results, assuming players have a desire to do well and have some competency for the game.

Therefor we can use double dummy analysis to tell us what will happen single dummy over many boards.

It does not matter whether a double dummy analysis will give the same result as single dummy on any specific deal, nor whether the result is obtained by the same method.

That is not the case but also not the point.

 

Rainer Herrmann

[gnasher]

The reason is if double dummy works as a good proxy for the expected result single dummy in general, there is no Bridge (or statistical) reason why the results should somehow be different when making some specific Bridge assumptions about distribution and HCP, but which are otherwise not related to the play of the hand itself.

What matters is only whether the number of deals in the simulation is high enough to give an approximation about the actual result for the total number of possible deals where this scenario can exist.

Of course the constraints can affect how well the double-dummy simulation models real-life. Suppose that I carry out a simulation where I specify that the declaring side has Axxx opposite KJ109. Would you expect the benefit of being double-dummy at notrumps to be the same as the benefit of being double-dummy with this suit as trumps? Obviously, it isn't, because in a notrump contract you may be able to delay playing this suit until you know how everything else breaks, but in a suit contract you can't. Hence in this example the advantage of being double-dummy in a suit would be greater than the advantage of being double-dummy in notrumps.

 

I am sure you know what double dummy analysis is bridge wise. The argument you use is Bridge related when the main argument is related to statistics, not Bridge.

You claim double dummy analysis is not real Bridge. Therefore you have little confidence in double dummy simulations.

No, I say that in this situation double-dummy analysis may not accurately reflect real bridge, because in this situation the ratio

(Advantage of being double-dummy at suit) : (Advantage of being double-dummy at notrumps)

May be different from the same ratio calculated over all hands, or calculated for a different set of hands.

 

But nobody claims this to be the case.

The claim is only that the result of double dummy analysis over many boards approaches single dummy real life results.

Therefor we can use double dummy analysis to tell us what will happen single dummy over many boards.

It does not matter whether a double dummy analysis will give the same result as single dummy on any specific deal.

Which part of that do you think that I didn't already understand?

[cherdano]

My judgement is that double-dummy in this situation favours the defenders at 3N, since the lead is so important: I think there will be many hands where declarer has 9 tricks of the top, and defenders 5, or where each side can set up that many tricks by losing the lead once.

So if double-dummy results favour playing 3N, then I think in real life the case is even stronger.

 

But my judgement already told me that playing 3N with 5332 opposite 4333 is better than playing 4M in your 5-4 fit, so I am not sure how much the double-dummy simulation helps.

 

Han's analysis, on the other hand, has the obvious problem of selection bias - it tells us that on hands where some world class pair chose to bid 3N, the 3N contract did better. That tells us that we would do well to imitate their strategies in choosing 3N, but unless what that strategy is, that's not all that helpful either. (Except for winning arguments on BBF against those who think you are wasting your time trying to find 3N on those hands.)

 

My views are that:

- If all you tell me are the shapes, and I can choose to play 3N or 4M in the 5-4 fit, on an auction that reveals nothing but the 5-card suit opposite a 1N opener, then choosing 3N is far superior.

- On some hands, the 4333 hand should choose to play 4M - e.g. with a xxx side suit, especially if he has already announced the fit.

 

I don't see how either the simulation or Han's analysis helps me much to validate or refute these views.

[GreenMan]

Han's analysis, on the other hand, has the obvious problem of selection bias - it tells us that on hands where some world class pair chose to bid 3N, the 3N contract did better.

 

It also tells us that on hands where some other world class pair chose to bid 4M, the 4M contract did worse.

[phoenix214]

It is technicly possible to avoid such fits if you adjusst stayman a bit. 2D says "I dont have a 4 card major or I have any 4333". And with some 5332 you just bid stayman so you can play 3NT on bad fits

[han]

I agree with Arend that the vugraph results are biased and it is hard to draw conclusions from them. The double dummy results are perhaps more reliable, even though they are double dummy. Fortunately both say the same thing: with 4-3-3-3 vs 5-3-3-2 you should play 3NT, even if you have a 5-4 fit.

 

Another possible test is to force a computer program to play lots of hand with these conditions, both in 3NT and 4M. I don't have a computer program that can do that.

[han]

It is technicly possible to avoid such fits if you adjusst stayman a bit. 2D says "I dont have a 4 card major or I have any 4333". And with some 5332 you just bid stayman so you can play 3NT on bad fits

 

If you compare this route to the transfer followed by 3NT route (promising 5332 shape) then you give away more information and you do less well because you will miss some good 5-3 fits when opener is not 4333.

[Fluffy]

who is saying that vugraph contains world class players only?

[han]

Bluecalm filtered the data to get tables where "elite pairs" were playing. So presumably at least one of the pairs at each table in the data set is world class.

 

I browsed through the hands and I knew all the names I saw.

[gwnn]

I do think that you should look for 3NT, but you should do it slowly and you should allow for the possibility of partner becoming declarer.

How does this work in practice? I assume we bid 2♠ (natural, points/length) and take it from there, say if partner bids 2NT we raise to 3, otherwise give up on 3NT?

[phoenix214]

You can use 2♣ to bid with 5M332 and spread out values, this makes so that you don`t want to play opposite a 3 card fit anyway,(3nt has better chances of making) so it isn`t that bad, and you can use the transfer and 3NT route with 5422 hands as well

[han]

How does this work in practice? I assume we bid 2♠ (natural, points/length) and take it from there, say if partner bids 2NT we raise to 3, otherwise give up on 3NT?

 

I don't remember the hand exactly, but it was a strong 3523. I think I would bid 3H offering partner a choice of games, if I played that.

[Zelandakh]

It is technicly possible to avoid such fits if you adjusst stayman a bit. 2D says "I dont have a 4 card major or I have any 4333". And with some 5332 you just bid stayman so you can play 3NT on bad fits

No need to adjust the initial responses to Stayman for this. There is a very old convention that was designed to achieve exactly this called SID (Stayman in Doubt). On its own SID is something of a waste for a bid but if you combine it with your strong raise call then you suddenly have a convention that is useful, worthwhile and will fit into the majority of NT structures.

[fromageGB]

I don't have a strong raise bid, what is that used for?

[Zelandakh]

For example, 1NT - 2♣; 2♠ - 3♥. Most pairs play this as a GF spade raise but you can bundle SID in with it. For hearts, most play the strong raise as a 2♠ rebid which gives ample space. I play transfers here instead and use 3♦ for the same thing - then the response structure is essentially identical to spades.

[han]

I have never heard of a pair using 1NT - 2C - 2H - 2S as a slam try in hearts, so I do not believe that most play this.

[cherdano]

Btw, I hope my post didn't imply that I disliked rhm's double-dummy simulation and Han's vugraph analysis. On the contrary, I always appreciate simulations and analysis that confirm what I already believe ;)

However, if I had started with the assumption that 4M is usually better than 3N on these hands, I am not sure the experimental data would convince me to change my mind :)

[MickyB]

Rainer, I'd be interested to see what results your DD analysis gives for a 2NT opening, so, say, 20 points opposite 5. My instinct is that 5332 opposite 3(433) is much closer here due to potential communications issues in 3NT.

[aguahombre]

I have never heard of a pair using 1NT - 2C - 2H - 2S as a slam try in hearts, so I do not believe that most play this.

I believe pairs who employ Reverse Fishbein and other conventions shown here might invert the meanings of 2♠ and 3♠ to save room.

[MickyB]

Justin,

The solution you describe above didn't address how you handle the unbalanced 5-card spade hand when partner bids 3H instead of 3D. Presumably, you must bid 3S (either 5 spades unbalanced or artificial heart slam try?), so this system does have the drawback of wrong-siding spades sometimes.

 

2N:3C, 3S with 4-4 majors

 

2N:3C, 3H:3S puppets 3NT with precisely four spades or a good 4H bid

 

2N:3C, 3H:3N shows five spades, looking for three-card support

 

 

This is very similar to what I play in the context of 2N:3C showing 4+spades and 2N:3D showing 4+hearts.

[PhilKing]

who is saying that vugraph contains world class players only?

 

Bad vugraph players? B-)

[pigpenz]

Don't agree, 3N is almost always 5332, and the other times it is 5422 with some honors in the doubleton. With 5431 or 5-5 or 5422 with a weak doubleton partner would just bid his second suit.

In a previous thread I ran a dealmaster pro analysis where someone had a super accept of a transfer

showing 4333......3NT def plays better than 4 major even on 9 card major fit