Bbradley62, on 2015-June-28, 20:10, said:
Is the ♦J play really best, or is it just a small sample size for simulations? Seems to me that playing from top wins whenever diamonds are 3-2 or East holds Qxxx, which should be clearly better than 50%.
If East holds Qxxx then neither play gains. When they break 3-2, the finesse gains when West has Qxx, the drop when East has Qx and neither gains over the other in other 3-2 breaks. West holding Qxx is slightly more likely (in a vacuum) than East holding Qx.
It is beyond my abilities to play by simulations, and I deal with most suit combinations by rote learning and memory. In this case I applied the old "8 ever, 9 never" often misused rule of thumb.
I believe that the more common beginner error is to cash one from the top to cater for Q singleton offside and then finesse. But that line is best only of you can then repeat a successful finesse, which requires South to have a third Diamond (and North one fewer) and sufficient entries. As West is more likely to hold Qxxx than East holding Q singleton, it is best (in a vacuum) to take two finesses (ie to cash one honour first only if there remains the possibility of 2 finesses afterward). This gains when West has Qx(x(x)) and loses (to playing from the top) when East has Q(x). West's holdings are a bit more frequent in total. I could have preserved an entry to South by deferring drawing the last trump (at minor additional risk of an adverse ruff), but there is no escaping the unchangeable fact that South was dealt only a doubleton Diamond.
It is not quite a vacuum here, but I am open to persuasion that we have sufficient additional information to depart from the bog standard play.
Psych (pron. saik): A gross and deliberate misstatement of honour strength and/or suit length. Expressly permitted under Law 73E but forbidden contrary to that law by Acol club tourneys.
Psyche (pron. sahy-kee): The human soul, spirit or mind (derived, personification thereof, beloved of Eros, Greek myth).
Masterminding (pron. m
s
t
r-m
nd
ing) tr. v. - Any bid made by bridge player with which partner disagrees.
"Gentlemen, when the barrage lifts." 9th battalion, King's own Yorkshire light infantry,
2000 years earlier: "morituri te salutant"
"I will be with you, whatever". Blair to Bush, precursor to invasion of Iraq