[NickRW]

Phil, on Jul 7 2010, 08:25 PM, said:

What I was hoping for was an analysis in response to my original question:

Quote

why it would make sense to ever put ourselves in an EV- situation by not bidding a % grand?

A sample position I was thinking about presenting to the math folk was this:

- We are in a match with a weaker team. Lets say we are, on average, 1 IMP / board better.
- The weaker team will NEVER bid the grand, but will ALWAYS bid the small slam.
- We are vulnerable, so we will win 13 if we make the grand and lose 17 if we do down.

I'm not sure you want a mathematical answer really - I don't feel like trying to provide one anyway.

I think what you're saying is that
1) You're the better team
2) Therefore you're likely ahead already
3) Therefore why put yourself in a position where you're risking a 17 imp loss when you can just cruise in the small slam

There is, of course, merit to that argument. OTOH:

1) Why do think you're the better team - is it not because you're better at these tricky decisions - if you don't put your better judgement to use then perhaps you're not that much better! Perhaps you could have done without this swingy board at the end of the match - but tough - you're in that situation now.
2) Weaker players don't NEVER bid 7 - nor do they ALWAYS bid 6 - those are both unsafe assumptions IMO

[Phil]

NickRW, on Jul 7 2010, 04:55 PM, said:

Phil, on Jul 7 2010, 08:25 PM, said:

What I was hoping for was an analysis in response to my original question:

Quote

why it would make sense to ever put ourselves in an EV- situation by not bidding a % grand?

A sample position I was thinking about presenting to the math folk was this:

- We are in a match with a weaker team. Lets say we are, on average, 1 IMP / board better.
- The weaker team will NEVER bid the grand, but will ALWAYS bid the small slam.
- We are vulnerable, so we will win 13 if we make the grand and lose 17 if we do down.

I'm not sure you want a mathematical answer really - I don't feel like trying to provide one anyway.

I think what you're saying is that
1) You're the better team
2) Therefore you're likely ahead already
3) Therefore why put yourself in a position where you're risking a 17 imp loss when you can just cruise in the small slam

There is, of course, merit to that argument. OTOH:

1) Why do think you're the better team - is it not because you're better at these tricky decisions - if you don't put your better judgement to use then perhaps you're not that much better! Perhaps you could have done without this swingy board at the end of the match - but tough - you're in that situation now.
2) Weaker players don't NEVER bid 7 - nor do they ALWAYS bid 6 - those are both unsafe assumptions IMO

Nick it seems to me that we need to hold a few things constant for a calculation, which is why I specified 'always' and 'never'. I didn't specify when the board was being played but if you want to make it the last board, then OK.

Even under your set of assumptions, it seems that one of the reasons we are the better team is our ability to bid excellent grands. If during most of the match we are bidding our 40% vul games in usual fashion, and things aren't going our way in that department, we very well may need the grand.

And yes, I am looking for the mathematical answer if anyone is up to it.

[zasanya]

Phil, on Jul 7 2010, 08:31 PM, said:

NickRW, on Jul 7 2010, 04:55 PM, said:

Phil, on Jul 7 2010, 08:25 PM, said:

What I was hoping for was an analysis in response to my original question:

Quote

why it would make sense to ever put ourselves in an EV- situation by not bidding a % grand?

A sample position I was thinking about presenting to the math folk was this:

- We are in a match with a weaker team. Lets say we are, on average, 1 IMP / board better.
- The weaker team will NEVER bid the grand, but will ALWAYS bid the small slam.
- We are vulnerable, so we will win 13 if we make the grand and lose 17 if we do down.

I'm not sure you want a mathematical answer really - I don't feel like trying to provide one anyway.

I think what you're saying is that
1) You're the better team
2) Therefore you're likely ahead already
3) Therefore why put yourself in a position where you're risking a 17 imp loss when you can just cruise in the small slam

2) Weaker players don't NEVER bid 7 - nor do they ALWAYS bid 6 - those are both unsafe assumptions IMO

Nick it seems to me that we need to hold a few things constant for a calculation, which is why I specified 'always' and 'never'. ..........

Even under your set of assumptions, it seems that one of the reasons we are the better team is our ability to bid excellent grands...................

And yes, I am looking for the mathematical answer if anyone is up to it.

Actually when I play a team match in which I believe my team is weaker I will bid a grand more aggressively rather than NEVER.
If I am up against a definitely weaker team who NEVER bid a grand and against whom i expect to win 1 imp /non grand slam deal then it seems mathematically correct never to bid grand against this team as i expect to win by at least 7 imps in the other 7 boards in a short 8 board match.This of course assumes that you do not mind the margin of winning.
If you want to extract maximum VPs then thats a different problem which cannot be solved without putting in other variables like how many vps you want.

[barmar]

mikeh, on Jul 6 2010, 06:15 PM, said:

So if we screw up at our table, it is wrong to automatically think that we are stuck....my view is that the other table owes us enough to cover at least one disaster and sometimes two....while when we are hot or the opps are having problems, we're the ones covering our teammates.

This is a good point. How many times have you gone back to your home table, apologizing to your teammates for losing the match, but they smiled and said "We got you covered", and you end up winning by 10 IMPs? You never know what's happening at the other table; unless you're playing against Meckwell-class opponents, they're just as capable of screwing up as you are.

So unless you really know your opponents, it's pretty difficult to estimate the "state of the match", and probably a bad idea to change your strategy based on it; you may just be digging yourself deeper when you didn't even need to.

But regardless of state of the match, the impact of a big swing on a short match is still quite significant.

[barryallen]

Phil, on Jul 6 2010, 12:16 PM, said:

bid_em_up, on Jul 6 2010, 11:58 AM, said:

Mike,

Should the above vary based upon the length of the match?  In a short match (i.e. six boards), I would expect that it would need a higher percentage of success in order to actually bid the grand.

Yes? No?

Why would you think this matters?

The greater the sample, the less the variance in the calculated odds, so the number of boards is significant. If you were tossing a coin 1,000,000 times it would not be a surprise that after 100 throws you came down with 60/40 and 500,020/499,980 after the million, although your odds on every throw will still be 1/2. For very small samples it pays to be overly aggressive if the intention is to win, less so if you are considering the percentages or where there is money involved.


These bridge odds are based upon you making the decision based upon the same percentages time and time again. Start changing your selection criteria throughout and it changes the original odds.

[campboy]

nigel_k, on Jul 6 2010, 10:56 PM, said:

Assuming the other side plays in game, the numbers are:
Vul minor: Gain 4 vs lose 12 so 75%
Vul major/NT: Gain 4 vs lose 13 so 76.5%
NV minor: Gain 3 vs lose 10 so 76.9%
NV major/NT: Gain 3 vs lose 11 so 78.6%

There's a factor of two error here. If you bid the grand and it fails you do score -11 on the board, but that is a loss of 22 compared to the +11 you'd get for making the small. So 88%.

[dburn]

I was hoping that some of the actual mathematicians would refer to the Parabolic Utility Function (oft quoted by Jeff Rubens, an actual mathematician, in the context of what to do in "sufficiently short" or "sufficiently long" matches).

Maybe they did, and I am too stupid to know that they did. But I still wish I knew what it meant.

[barryallen]

dburn, on Jul 10 2010, 06:17 PM, said:

I was hoping that some of the actual mathematicians would refer to the Parabolic Utility Function (oft quoted by Jeff Rubens, an actual mathematician, in the context of what to do in "sufficiently short" or "sufficiently long" matches).

Maybe they did, and I am too stupid to know that they did. But I still wish I knew what it meant.

Just go and look at the results of tournaments on BBO where you have a set of 8 boards played by 50 pairs. The chances of you winning by adopting standard percentages are minimal, although your percentages will be well in.