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.