[kgr]

IMPs

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You play 3NT after East opened 1NT (9-11 HCP) and West transferred to spades.
West leads ♠4.
Do you play small or high from dummy?

[mgoetze]

This doesn't seem particularily controversial? I mean, first of all, we have 26, if East has 9, then ♠KQ is the absolute maximum West can have in terms of high cards. East could have 10 or West could have some random Jack and then ♠KQ is already impossible, so East is a big favorite to have at least one spade honor. Meanwhile West has 2/3 of the spade cards we haven't seen, so he is favorite to have the 10. Seems pretty obvious to me to play the 8 or 9.

[kgr]

mgoetze, on 2014-December-28, 07:03, said:

This doesn't seem particularily controversial? I mean, first of all, we have 26, if East has 9, then ♠KQ is the absolute maximum West can have in terms of high cards. East could have 10 or West could have some random Jack and then ♠KQ is already impossible, so East is a big favorite to have at least one spade honor. Meanwhile West has 2/3 of the spade cards we haven't seen, so he is favorite to have the 10. Seems pretty obvious to me to play the 8 or 9.

You didn't mention West's DBL. Do you consider it unimportant?

[nige1]

rubbish deleted

[whereagles]

Small.

You're playing for LHO with KT+ or QT+, which is roughly twice as likely as KQ+.

[Fluffy]

whereagles, on 2014-December-28, 13:17, said:

Small.

You're playing for LHO with KT+ or QT+, which is roughly twice as likely as KQ+.

Not fully accurate, if ♠J is wrong we have a backup ♥J finesse while if ♠9 is wrong there is no back up finesse since the ♥J must be wrong. So 1/3 or 1/2 vs 2/3 is equal in theory.

We could count all honor combinations.

-♠KQ jack wins
-♠K low wins 4/5 times when ♠10 is onside
-♠K + ♥J anything wins
-♠Q + ♥J anything wins
-♥AJ anything wins
-♥A Anything wins except if they duck ♣Axxx and manage to score 2♠, 2♣, 1♥, but this position still makes no sense given the double.
-♣A low wins, but double makes no sense
-♣A + ♥J anything wins


I am probably missing some combinations, but so far the jack looks a tiny bit better asuming the double cannot be done on ♠10xxxx.

The problem is that we are assuming 2 things that don't need to be true: double shows a willing to get a spade lead, and RHO will never upgrade or downgrade into the 9-11 range. These assumptions are probably far from certain, so playing low will probably be better in practice.

[kgr]

Thank you all.
RHO had ♠Tx and all other honors in ♥♦♣.
I played ♠9 and ended -1.

[Free]

If LHO has ♠KQ he can never cash them. All we have to do is duck the first trick. Small is obvious. When RHO wins ♠T and continues with the ♠K we can duck again, blocking the entire suit.

[kgr]

Free, on 2014-December-29, 05:46, said:

If LHO has ♠KQ he can never cash them. All we have to do is duck the first trick. Small is obvious. When RHO wins ♠T and continues with the ♠K we can duck again, blocking the entire suit.

Not so obvious. If LHO has ♠KQ then RHO has the other honors and only 8 tricks can be made if you duck the first trick.