[pescetom]

With the tendency towards more aggressive opening I guess it is increasingly infrequent that all four players pass a given hand, and even more rare that this occurs at most tables. Nevertheless, three times this week at my table all four passed, and every time the dealer's side came off worse in matchpoints, two of them bottoms. This is obviously just a fluke, but it set me wondering about how frequent is a hand where all four players pass at (say) 2 or more tables, and how the outcome in matchpoints is distributed.

Does anyone (hrothgar?) have numbers on this, or the possibility to calculate them? IIRC the probability that no hand in a deal has 12+ HCP is around 3%, but obviously the frequency of all four pass will be less. My guess would be below 1%, but also quite likely to be a top/bottom.

[Vampyr]

 pescetom, on 2019-May-11, 08:34, said:

With the tendency towards more aggressive opening I guess it is increasingly infrequent that all four players pass a given hand, and even more rare that this occurs at most tables. Nevertheless, three times this week at my table all four passed, and every time the dealer's side came off worse in matchpoints, two of them bottoms. This is obviously just a fluke, but it set me wondering about how frequent is a hand where all four players pass at (say) 2 or more tables, and how the outcome in matchpoints is distributed.

Does anyone (hrothgar?) have numbers on this, or the possibility to calculate them? IIRC the probability that no hand in a deal has 12+ HCP is around 3%, but obviously the frequency of all four pass will be less. My guess would be below 1%, but also quite likely to be a top/bottom.

What would be interesting is to see which side generally profits when a shaded open bid in 3rd or one based on Pearson points in 4th is made.

[barmar]

Here's an old thread about Pearson points:

https://www.bridgeba...d-distribution/

Larry Cohen suggests an amusing alternative to the Rule of 15, Cohen's Rule in Fourth Seat (CRIFS): If you have a marginal opening, evaluate your opponents -- pass if they're strong players, open if they're weak.

https://www.larryco....nter/detail/315

[Tramticket]

 pescetom, on 2019-May-11, 08:34, said:

... three times this week at my table all four passed, and every time the dealer's side came off worse in matchpoints, two of them bottoms. This is obviously just a fluke ...

It isn't obvious to me that it is a fluke.

Only one of the four players passed, knowing that this would result in a throw-in - the fourth player. The other three players at the table may have passed for various reasons, but they would not be expecting their pass to result in a throw-in. The fourth player has a straight choice between bidding and passing, knowing that a positive score will improve the MP expectancy (compared with zero for a throw-in) and a negative score will reduce the MP expectancy.

We can assume that the player in 4th seat will only choose not to pass if he/she expects a positive return on average based on the 13 cards they can see and a knowledge that the HCPs other hands are evenly split. You would expect a moderately competent player to choose based on methods (including, say, the quality of the spade suit) their call to give a positive EV.

[pescetom]

 pescetom, on 2019-May-11, 08:34, said:

Nevertheless, three times this week at my table all four passed, and every time the dealer's side came off worse in matchpoints, two of them bottoms. This is obviously just a fluke, but it set me wondering about how frequent is a hand where all four players pass at (say) 2 or more tables, and how the outcome in matchpoints is distributed.

 Tramticket, on 2019-May-13, 09:10, said:

It isn't obvious to me that it is a fluke.

Sorry for a clumsy phrase, the fluke is that it happened 3 times in a week. I am doubtful about the fact that every time the dealer's side came off worse in matchpoints - I imagine that this should be 50% for a large enough sample independent of specific players, but do not take that for granted. It is my impression that it is quite frequent for the matchpoint score to be bottom/top in the case where other pairs have opened the same hand, but I do not take that for granted either. I am interested in all three of these probabilities.

 barmar, on 2019-May-13, 08:13, said:

Larry Cohen suggests an amusing alternative to the Rule of 15, Cohen's Rule in Fourth Seat (CRIFS): If you have a marginal opening, evaluate your opponents -- pass if they're strong players, open if they're weak.

"Add 1 if they are weak" is a practical way to apply this reasoning.

 Tramticket, on 2019-May-13, 09:10, said:

ly one of the four players passed, knowing that this would result in a throw-in - the fourth player. The other three players at the table may have passed for various reasons, but they would not be expecting their pass to result in a throw-in. The fourth player has a straight choice between bidding and passing, knowing that a positive score will improve the MP expectancy (compared with zero for a throw-in) and a negative score will reduce the MP expectancy.

We can assume that the player in 4th seat will only choose not to pass if he/she expects a positive return on average based on the 13 cards they can see and a knowledge that the HCPs other hands are evenly split. You would expect a moderately competent player to choose based on methods (including, say, the quality of the spade suit) their call to give a positive EV.

In 2 of the 3 occasions mentioned I was 4th seat and it didn't meet my criteria, which include Rule of 15. But in 1 of those opponents opened at most other tables. So it wasn't just me and I don't think I was making unusual choices. It's just the first time this showed up on my radar as a signficant issue and I am curious to know the numbers.

[barmar]

I don't think I ever count Pearson points these days. My usual criteria for opening a minimum hand in a minor in 4th seat is whether I have a hand that can pass whatever partner responds. This might end up being similar to the Rule of 15, since I'll usually be 4-4 or 4-3 in the majors.