awm, on May 13 2010, 01:07 PM, said:
blackshoe, on May 13 2010, 12:21 PM, said:
awm, on May 13 2010, 12:32 PM, said:
In many ways this case is actually easier, because a crazy bid was made that "can't possibly be right" without the UI. It should be routine to roll such fliers back.
It hesitated. Shoot it.
People say this as if it means something. But it really doesn't.
You have the following sequence of events:
(1) There was a hesitation.
(2) A crazy bid was made that no good player would ever make without the hesitation; the a priori chances of this bid working given the auction must be vanishingly small.
(3) The hesitation dramatically increases the chances of the crazy bid working (even if still less than even odds).
(4) If the player in question is able to get a good "read" on his partner's reason for hesitating, then the chances of the crazy bid working given this read could easily be greater than even odds.
(5) The crazy bid worked.
What more do you possibly need to adjust? It seems more like the people arguing the other way are expressing an attitude that
taking advantage of partner's BIT to reach better contracts is "just bridge.".
Adam: most of your posts make sense to me, but this last one doesn't. I really think you are screwing up when you assert that a priori the leap to 6
♥ had a 'vanishingly small' chance of being successful. Are we even looking at the same hands?????? I would conservatively estimate the chances of making 12 tricks opposite a smooth raise at 20% or more. I am not going to waste time by giving examples: everyone here can quickly come up with hands for responder on which slam has play and on which no-one would try for slam as responder.
Then you assert, with zero evidence, that opener may have got a 'good read' on what the hestitation meant. That argument is crap.
In real life, we MIGHT know whether that may have been the case, and as a committee we'd ask a lot of questions aimed at that issue, but it is wrong to raise this as an argument in favour of an adjustment when we don't have ANY reason (other than the horrific rule of coincidence) for assuming it. And if we had actual evidence, then that would probably be all we'd need in order to make an adjustment.
As for your assertion, made numerous times, that the hestitation, even if we can't define whether made from weakness or strength or choice of strain issues, makes blasting more attractive: well, some pretty good players disagree with you on that and even your approach only shows a 'dramatic' increase because your numbers are biased in favour of that conclusion....and you admit that your numbers are pure guesses.
A lot of your argument turns on assuming that the chances of slam making on a non-hesitation auction are somewhere between vanishingly small (your current position) and 10%...your previous position. And much of the rest is based on the assumption that the odds go up to 60% on the borderline slam hands.
Change the a priori to 20%, and the arithmetic greatly reduces the perceived benefit arising from the BIT.
In addition, I think we agree that the BIT is most probably induced by holding one of four hand-types: P/4
♥; 3N/
♥; 3
♠/4
♥; slamtry/4
♥.
Assume that they occur with equal frequency (statistically, when we hold 17 hcp, partner will far more often hold one of the other 3 than the slam try, so this assumption is in your favour).
Assume that opposite the P/4
♥ hand the chances of slam are essentially nil, and that there are some risks that we get doubled and go -300 (I will use NV numbers here), such that the average loss by bidding slam on those hands will be, say, 11.5 imps.
Assume that opposite the choice of strains hands, the chances of slam are reduced slightly from the a priori odds....the a priori odds are based on a set of hands that include near slam try holdings, and those are not in the sets of choice of games. So we will assign a 10% chance of the neutral hands making slam.
On the strong 25%, slam makes 60%, resulting in a gain on average of 2.2 imps per board, while a priori bidding slam results in a loss of 6.6 for a swing of 8.8
On the weak 25%, slam never makes and we lose 11.5 imps as per the above. A priori our loss is only 6.6, so we are worse off by 4.9 imps
On the neutral 50%, we lose 8.8 by bidding with the BIT, and 6.6 a priori, so we are worse off by 2.2 imps.
Summed over 40 boards, 10 of each category, we win 88 imps when partner has the strong hand, lose 49 when he has the weak, and lose 44 when he has the borderline hand.
Net, bidding slam after the BIT costs us 5 imps over 40 boards, compared to our expectation with no BIT.
Are my numbers better than yours? I happen to think they are, but so what? If you agree that a reasonable expert could adopt this view, then it becomes clear that it is reasonable for an expert to conclude that the BIT doesn't demonstrably suggest bidding slam.
BTW, it is not difficult to nudge these figures to show that the BIT dramatically diminishes the chance that slam makes. Lower the likelihood of the slam try hand to 20% as an example....and we win only 70 imps (approx) while losing about 100.
Increase the a priori odds of slam making (I repeat: did you see how good that E hand is?), and the numbers swing again towards my view.
'one of the great markers of the advance of human kindness is the howls you will hear from the Men of God' Johann Hari