Who is preempting whom?

[bluecalm]

In this case, unlike poker, the only place where pass beats both X and 5♥ is if ♣ make at least 5 and ♥ is down at least 3. Maybe it is the case that both 5♣ makes at least 11 tricks and 5♥X makes no more than 8 tricks at least 50% of the time, but if not, then it is hard for pass to be the right bid (even if figuring out what is the right bid between X and 5♥ is hard).

 

JLall's analogy was right.

Your analysis assumes you know your opponents "cards" so if your hand is better you should raise (because maybe he will call with his weaker hand) and if your hand is worse you should fold (obviously).

 

Back to bridge terms, you assume that you are either down 3 in 5♥dbl or you are not and that they are making or not. Obviously you don't know that when making your decision.

Very simple example is this:

-they are always making

-you are down 3 in 40% of cases

-you are down 2 in 60% of cases.

 

Let's compute EV of passing versus going to 5♥ doubled.

 

in 40% of cases 5♥ loses 5imps (800 - 620 = 180 = 5imps)

in 60% of cases 5♥ wins 3imps (620 - 500 = 120 = 3imps)

 

So EV of going to 5♥ is -40% * 5imps + 60% * 3imps = -0.2imps.

 

So 5♥ is correct most of the time but passing is right action (and if they are sometimes losing 4♠ the EV difference will be much bigger)

This example is very simplistic but good enough to discard your analysis I think.

[gwnn]

you gotta be a little more careful, it's matchpoints.

[bluecalm]

you gotta be a little more careful, it's matchpoints.

 

Yeah right. It's easy to construct similar example for matchpoints though.

For example it's enough if going from +100 to +200 will be worth 30% (from 70% to 100%) and going from - 620 to -790 will be worth 50% (from say 50% to 0%)

[aguahombre]

Actually -950 or 1400 (if xx), but same zero.

 

Unless they only make 5, then it is the same zero, too.

[Jlall]

In this case, unlike poker, the only place where pass beats both X and 5♥ is if ♣ make at least 5 and ♥ is down at least 3. Maybe it is the case that both 5♣ makes at least 11 tricks and 5♥X makes no more than 8 tricks at least 50% of the time, but if not, then it is hard for pass to be the right bid (even if figuring out what is the right bid between X and 5♥ is hard).

 

JLall's analogy was right.

Your analysis assumes you know your opponents "cards" so if your hand is better you should raise (because maybe he will call with his weaker hand) and if your hand is worse you should fold (obviously).

 

Back to bridge terms, you assume that you are either down 3 in 5♥dbl or you are not and that they are making or not. Obviously you don't know that when making your decision.

Very simple example is this:

-they are always making

-you are down 3 in 40% of cases

-you are down 2 in 60% of cases.

 

Let's compute EV of passing versus going to 5♥ doubled.

 

in 40% of cases 5♥ loses 5imps (800 - 620 = 180 = 5imps)

in 60% of cases 5♥ wins 3imps (620 - 500 = 120 = 3imps)

 

So EV of going to 5♥ is -40% * 5imps + 60% * 3imps = -0.2imps.

 

So 5♥ is correct most of the time but passing is right action (and if they are sometimes losing 4♠ the EV difference will be much bigger)

This example is very simplistic but good enough to discard your analysis I think.

There was a thread once where I made a post similar to this. At MP it's a little more complicated, but the same point applies.

 

Mbodell:

 

There are going to be a ton of decisions where you're not sure who has what, and what their chances are of making or what you could have made. In those times of uncertainty, it is my view that it is very wrong to force yourself to commit one way or the other to "they are making too often" or "they are going down too often."

 

Not only can you come up with a (albeit contrived) mathematical model where the percentages of everything break down such that it's right to pass, it just seems like common sense and "bridge" to me to accept that you don't have perfect information, and on this hand you have bits and pieces of defense but not enough to warrant making a strong view about your chances. The times when it's best to pass are the times when things are most uncertain.

 

This hand is a good example. Are they making? Who knows, it was a pretty random auction, our stiff queen might add a trump trick somewhere, our SK might be a trick, and we have no idea what their hands look like. Saving is a complete gamble to me (that would be my choice over X if I had to pick one).