3

If a contract depended on say, a finesse, most good players would look for plays that would give a better than 50-50 chance of succeeding. (Unless the finesse was marked by the bidding or early play.)

Most good players would make, or consider making, a safety play to guard against a 4-1 split (except maybe in matchpoints). This occurs with a greater than 28% frequency (or 14%+ if it was relevant with the singleton on one side and not the other).

But I read of a situation in a tournament where a world class declarer took an inordinately long time to study the play of a hand, to the point where his opponents called the tournament director (TD). When the TD asked the player why, the player answered that he had just worked out a way to make the hand against a distribution with only a 2% chance of occurring (a 5-0 trump distribution with the 5 "offset" a finesse).

He looked like a genius when the relevant opponent admitted to having that hand. Apparently, there was little time to play the game out, but the TD awarded the point to the player after the player described his game plan and the opponents conceded, showing down their hands. All the other declarers on that board went down.

Is that unusual? Do good players routinely study ways to guard against 2% chances over the board? Or do most players have a higher threshold, say in the 5%-10% range?

4

2%? I don't think most would worry about 2% on most hands, because most hands you'd be losing a higher percentage of the time to protect against the lower.

But yes, in this kind of case it's not uncommon to protect against 5-0 splits. While it's not common, 2% is 1 in 50 hands, meaning it might come up a few times in a weekend; the difference between a highly experienced player and a top-tier player might only be a few hands, and those would be some of them.

It really comes down to the hand. If the hand is played at IMPs (where making the hand is paramount, rather than overtricks), and it's solid for 4-1 or 3-2, then there's no reason not to explore 5-0 split lines. I've certainly done it a number of times before, and I'm hardly a world class player.

I suspect your story is a bit of an apocryphal one, given the description of the actions after the tournament director was called are inaccurate to what would really happen at a tournament (slow play involves slow play warnings, and eventually board penalties, but would not modify the results of a hand; the tournament director would not "award the point" either, it would be up to the opponents to accept the claim or not, if a claim was indeed what was made). But the actual details - that a world class player considered his line of play for several minutes in order to find a safe line against a 5-0 split - are entirely reasonable, if a bit boring compared to the dramatic telling.

1

In an IMPs situation, you can calculate the IMP odds to determine what the right thing to do is. Let's work an example.

The declarer is in 4H vulnerable. Line of play 1 makes 5 most of the time, but x% of the time goes down 1. Line of play 2 always makes 4. Let us assume that your opponents are in the same contract will always take the safety play. Line 1 wins 1 IMP for the overtrick (100-x)% of the time, but loses 12 IMPs for going down x% of the time. 1 * (100 - x)% = 12 * x% when x = ~8%. So if that's the situation, you should only take line 1 if it has less than 8% chance of going down.

Most situations are a bit more complicated but the principle is the same.

  • I don't think that's what OP is asking. OP is asking how often people bother to spend the time to figure out a line for a 2% likely play, not how people compare different lines of play with different probabilities. – Joe Jan 9 '17 at 16:37
  • You can judge whether thinking about a 5-0 break is worthwhile by figuring out the odds of the break and the likely number of tricks a safety line would take. – ruds Jan 9 '17 at 16:41
  • Yes, you certainly can, but OP is asking if people do, not if it is possible to. – Joe Jan 9 '17 at 16:42
  • A good player takes these things into account. – ruds Jan 9 '17 at 16:43
  • 1
    @Joe: I see this answer by ruds as an answer to the title of the question. The other question, "do good players do that", is a pointless question IMO. Answer is, yes depending on the situation. Now what does that get us? Anyway... – Aryabhata Jan 26 '17 at 21:25

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