Percentages & Intuition

[Finch]

This hand came up in the last round of the European Schools event.[hv=w=skhaq9xdkqjxcajxx&e=saq8xxxhkxdaxxckx]266|100|Scoring: IMP[/hv]

 

The table I was commentating at bid to 7S, which clearly isn't the best contract.

I claimed at the time that 7NT was clearly the best spot.

At least one spectator suggested that 7D was best (taking a heart ruff in the dummy).

 

My suggestion has a serious problem.

 

7NT is absolutely huge double dummy, I make it over 92%. However, it's much less good single dummy, because either you have to give up on various squeezes early on to clarify the position or you have to be a complete god at reading early discards.

 

So let's consider the simple line in 7NT of spades 3-3 or the club finesse.

 

So here's a question for your intuition. Don't work it out in detail, but suppose you were at the table and simply had to decide which contract to bid knowing both hands.

 

Which is the better contract, 7D (heart ruff in dummy) or 7NT (simple line)?

[coyot]

It's a strange question - I can hardly decide at the table knowing both hands ;)

 

I would hardly decide for 7♦ unless I knew about Axx in diamonds and two doubleton kings :).

 

But when it comes to odds, 7♦ needs diamonds 4-2 or 3-3 and hearts 4-3 or 5-2 with the doubleton being on the same side as doubleton diamond.

 

Good diamond break: 84%. Good hearts break: 52%. Total: 43%.

Add for the extra chance of both red doubletons on same side: (30% and 48% and 50%) 7%. (Actually significantly less, because the 30% and 48% are odds for the 4-2 and 5-2 divisions, but the chance that if those two divisions occur and the same time in the SAME hand is much less than 50%).

 

Rough estimate would be something below 50%.

 

7NT: 35% for 3-3 plus 50% of the remaning 65% (finesse) = more than 60%, clearly superior.

[Walddk]

So let's consider the simple line in 7NT of spades 3-3 or the club finesse.

 

<snip>

 

Which is the better contract, 7D (heart ruff in dummy) or 7NT (simple line)?

7NT is better than the simple line you point out. ♥J10 or J10x in either hand will also give you 13 tricks if spades don't behave. Then you don't even need the club finesse.

 

7NT is clearly better than 7♦. Ruffing a heart is dangerous every time one defender has a doubleton. Then you will have to rely on diamonds to be 3-3, because you must ruff with the ace.

 

Roland

[Finch]

7NT is better than the simple line you point out. ♥J10 or J10x in either hand will also give you 13 tricks if spades don't behave. Then you don't even need the club finesse.

Oh yes, indeed.

 

Question 2:

How good is 7NT, and what is the right line, if you assume you cannot tell anything from opponents' carding?

 

At the table, I'm fairly certain I would cash 4 diamonds, the SK, 3 hearts, the CK then the SA discarding a club and the SQ, planning to discard the heart. If South started with 5 hearts and North 4+ spades, I will know that a double squeeze has worked. In some other cases I will know that the club finesse cannot gain and will also pick up Qx offside. These squeeze cases don't actually add a huge amount to the "simple line" though obviously everything helps.

[keylime]

7NT is standout for some interesting reasons.

 

1. Lotta squeeze potential. Might even see a criss-cross or stepping stone squeeze.

2. Are diamonds really going to be 3-3/4-2? Probably not.

3. Spades if 3-3, is a source of tricks.

 

It just "feels" right to me.

[coyot]

I told you ;), 35% plus 65%/2 = 67%. (plus the additional chance of J10x in hearts in one hand... (Which would be 52% * 3/7 * 2/7 if I am not mistaken, approx 5% total).

 

In layman terms, good enough (it goes over the 70% which I remember seen as a good grand requirement.)

[Walddk]

1. Lotta squeeze potential. Might even see a criss-cross or stepping stone squeeze.

Stepping stone squeeze must be a typo, Dwayne. It's an endplay squeeze where a defender serves as a stepping stone in order to reach a stranded winner.

 

We do not want to endplay anyone in a grand slam :)

 

Roland

[whereagles]

I'm not sure if this isn't an academic question... at table no one (bar relay bidders) would find the moysian 7♦.

 

I do think 7♦ is the best contract because it's much easier on your nerves :)

[Fluffy]

it seems 7NT is better, but at 7♦ appears a very common problem, is it better to ruff a ♥ directly, so if north has 4♦ and 2♥ we can overruff him and succeed, or is it better to cash 2 trumps, and hope for double shortness on someone?.

[Walddk]

Here is how Bar Tarnovski - Dror Padon from Israel bid 7♦:

 

1♦ - 1♠

2♥ - 2♠*)

3N - 4♦

4♥ - 4N

5♠ - 5N

6♣ - 6♦

7♦ - p

 

*) Forcing

 

1444 hands are difficult to bid accurately, so Padon obviously thought that Tarnovski was 4-5 in the reds. 5NT was a grand slam try, guaranteeing all key cards and ♦Q. The 6♣ response was not enough, and Padon signed off.

 

Tarnovski tanked for a while before he raised. After all, he had considerable extras and should perhaps have jumped to 7 over 5NT already.

 

He got a trump lead, won the ace and cashed another round of trump. Then a heart to the king and another one back to the ace. He then cashed ♠K before ruffing a heart. As it was, he could not go down no matter which line he took.

 

By the way, I just looked it up. West did not have ♥9. He had AQ7x. East had K9. Frances rotated the deal to begin with (it was a NS hand), but that is insignificant.

 

Roland

[Double !]

I am probably the worst declarer of anyone who posts: totally capable of going down 1 or 2 when everyone else is making overtricks. But, sometimes I can work things out and play a hand well (when awake), sometimes for the wrong reasons.

 

My first reaction to this hand was 2-fold: 4-2 breaks occur more often than 3-3, hence the potential for an overruff in 7D. Secondly, there appear to be at first glance so many things that could go right in NT and as well as potential squeeze positions. There seem to be sufficient entries. and if all else fails, there is still the possibility of a club finesse.

7NT

[han]

7NT is standout for some interesting reasons.

 

1. Lotta squeeze potential. Might even see a criss-cross or stepping stone squeeze.

2. Are diamonds really going to be 3-3/4-2? Probably not.

3. Spades if 3-3, is a source of tricks.

 

It just "feels" right to me.

1. See you Roland's post.

 

2. Yes, they probably are.

 

3. Ah, that proves it!

 

But I must say 7NT also feels right to me.

 

 

Coyot's odds calculation is also incorrect. If north has a heart and 3 or more diamonds, you are still good in 7D as you can safely overrufff with the ace.

[coyot]

Coyot's odds calculation is also incorrect. If north has a heart and 3 or more diamonds, you are still good in 7D as you can safely overrufff with the ace.

Oh, I forgot about that...

 

So, it adds (15% for the 5-2 heart break on the right side)*(conditional probability of diamond break not being 4-2 on the same side (trump promotion).

 

I started the calculations wrong way, then.

 

Should be:

 

1) hearts 4-3 and diamonds no worse than 4-2 (43%)

 

plus

 

2) hearts 2-5 and diamonds no worse than 4-2 or 3-3 (but not 2-4).

(15% * (35%+a somewhat more more than 24%), roughly 10%).

 

Still, the success rate for this slam is significantly worse than 7NT. (Roughly 55% vs.. 70+%)

[keylime]

Roland,

 

What was I thinking? :-) Of course there's no stepping stone, duh. See what happens with no coffee?

 

On a rethink, what about potential of a certain guard squeeze....

[Led]

i guess that 7NT is clearly a better contract

first because they are so many possibilities : Spades ok

or ♥J10 short, or any squeeze

but also because you cannot go down before trick 12 !

players never like to go down on first trick <_<

 

and sometimes defense isnot so perfect (depends were is dummy?)

and gives you a clue

also on some distribution you may find that you have to take a 2nd round finesse in ♥

let say you know North has 6♠ and 5♦ and 1♣ and play the ♥10

:P

 

 

something else : why do everyone wants ti ruff a ♥ in dummy?

a club ruff seems better to me

not because clubs divide 43 more often than hearts

but because you may see the Queen fall on first or second round of club !

a -not so low- improvment

 

Edouard , new in the forum

[coyot]

something else : why do everyone wants ti ruff a ♥ in dummy?

a club ruff seems better to me

not because clubs divide 43 more often than hearts

but because you may see the Queen fall on first or second round of club !

a -not so low- improvment

 

Edouard , new in the forum

A good point, man. This increases the chance of 7♦ making, because the contract success rate is enhanced by the J10x ♥ (which works for 7NT) and the (albeit small) odds of Qx in clubs on either side. (approx. 2/7 of 30%).

[Walddk]

By the way, I just looked it up. West did not have ♥9. He had AQ7x. East had K9.

Maybe have a look at this (again). I wrote that yesterday, so forget about J10 or J10x hearts.

 

Roland

[Led]

By the way, I just looked it up. West did not have ♥9. He had AQ7x. East had K9.

Maybe have a look at this (again). I wrote that yesterday, so forget about J10 or J10x hearts.

 

Roland

how about J108 then ?

<_<

 

ok this is a small percentage!

 

Edouard

[han]

Good points Edouard!

 

and welcome to the forum :D