[phoenix214]

I decide to do some calculation to some calculation to see what is the risk of playing slams in imps. I compared these situations - Slam makes, other table does n `t play slam. Slam makes or it is down 1(t.i on a finesse). Comparing these situations i noticed that besides the fact that this makes large swings it pays off to put bid a slam that is on a finesse. All slams if they make give your team the same amount of imps that if you go down one your opps get. Well but then i noticed one interesting thing. If we look at a minor suit slam non-vulnerable. If it makes, you get 920 compared to 420 which is 500 difference which is +11 imps. If the slam goes down you get -50, opps get 400, difference is 450 which equals 10 imps. If i get this right - that means that bidding a minor suit small slam NV is good if you don`t have an Ace + it is on finesse. Can anybody correct me if im wrong?

[lalldonn]

Technically you are correct, but there is no way you could ever apply it at the table. You have to KNOW the opponents are in 5 of the minor at the other table, and KNOW your slam is exactly on a finesse. Maybe a ruff can beat you. Maybe 5-0 trumps can beat you. Maybe the suit is AQTxx and Jxx and both partners know each other's length but not about the J/T. Maybe the other table is only in a partscore(!), or 3NT, or overbid to a grand slam, or is in a 4-3 major suit fit. Maybe your teammates at the other table collected 800 against something so you have 3 to win but 13 to lose. Maybe you have a slight extra chance like AJxx opposite singleton playing for two tricks. Maybe the slam will be doubled. Maybe you think they will make the wrong lead a lot, making the finesse for an overtrick. Maybe the finesse is into declarer's hand and they have a chance to lead away from the honor on opening lead. etc etc etc etc

[phoenix214]

Well sure, there are always other possibilities, i was just started to think about such possibilities because of the way how you should bid games in imps - t.i. aggressive so i decided to do a little calculation to see how this applies to slams, and is it true that we shouldn`t bid sound slams that have to be like 60-70% making chances

[jogs]

Sounds good, but in real life it doesn't work. One never
knows for certain the exact situation. Even at the highest
level when one team is in slam and the other isn't, the
non slam team has been the net winner.

[Codo]

This surprises me.


Where do you have your data from?

[Zelandakh]

One of Culbertson's rules (from the 30s and 40s):
Bid a slam if it is known to be at worst 50%.
Do not bid a slam if it is known to be at best 50%.

The other rule he had for slam bidding, less relevant to this discussion but still potentially useful, was:
Bid the slam if a perfect minimum would make it laydown.

Obviously Ely played in an era where rubber bridge dominated. Nonetheless, his rules are probably close enough to the reality of IMP duplicate to still be of interest, at least to normal club players (which was the main audience for his books).

[PhilKing]

Zelandakh, on 2013-February-25, 08:30, said:

The other rule he had for slam bidding, less relevant to this discussion but still potentially useful, was:
Bid the slam if a perfect minimum would make it laydown.

Warning! Dangerous misquote.

The advice was that you are worth one try if the perfect minimum would make it laydown. The corollary is that if you need a perfect maximum, do not even make a try.

[Zelandakh]

You are right of course, but in my defence it is 30 years since I last read it.

[jogs]

Codo, on 2013-February-24, 02:11, said:

This surprises me.


Where do you have your data from?

I tracked a few of JLOGIC's team matches which were posted on BBO.
Also other team matches from those events.

[PhilKing]

jogs, on 2013-February-23, 20:21, said:

Sounds good, but in real life it doesn't work. One never
knows for certain the exact situation. Even at the highest
level when one team is in slam and the other isn't, the
non slam team has been the net winner.

What are you going to do with this information (which is wrong, as it happens)? Say you KNEW opponnents were in slam - do you suggest stopping in game based on that evidence alone?

Let me make a stat up off the top of my head - when two top class pairs bid slam, there is an 80% chance it is cold (which is approximately true). By staying out of slam does it become odds against? You can see the logical disjoint - if you bid slam it will almost certainly make, yet if you don't apparently it is probably going off.

[jogs]

PhilKing, on 2013-February-25, 14:59, said:

What are you going to do with this information (which is wrong, as it happens)? Say you KNEW opponnents were in slam - do you suggest stopping in game based on that evidence alone?

Each side holds 32 or more points one out of 150 boards.
Skewed patterns makes slams possible about one out of 40 boards.
Some pairs bid slams nearly one out of 20 boards.

Do a real study. Prove that I'm wrong.

You never know whether opponents have bid slam.
There are frequent observations which one team bid
slam down one when their opponents didn't even find game.

Quote

Let me make a stat up off the top of my head - when two top class pairs bid slam, there is an 80% chance it is cold (which is approximately true). By staying out of slam does it become odds against? You can see the logical disjoint - if you bid slam it will almost certainly make, yet if you don't apparently it is probably going off.

On only one out of 150 boards is it clear to
bid slam based on power(points).

[PhilKing]

jogs, on 2013-February-26, 09:48, said:

Do a real study. Prove that I'm wrong.

OK. It took a few hours, but here you go. I chose the Spingold for my statistical study, since all the finals are available since 1996 with the exception of 2002. I have also included one semi-final where possible, so about 1500 deals all told. I will not regard the findings as definitive untill I have examined closer to 10K deals (which I will at some stage).

I collated four sets of statisitics:

1. Both sides bid slam.

39 times slam made at both tables. 9 times one side made slam and the other went off, usually because they were in different slams. 4 times both sides bid slam and went off. That is a raw total of 87 successful slam ventures and 13 unsuccessful - higher than the 80% top of my head figure.

On highly competitive auctions it was wrong to bid slam on two times out of three (these are treated separately for various reasons).

2. Only one side bid slam.

More often, only one side reached slam. On broadly uncontested auctions, slam was successful 45 times and failed 21 times. On highly contested auctions, bidding slam was right twice, wrong three times, and had an unclear outcome twice.

This evidence utterly contradicts the myth of expert slam overbidding. They are not bidding enough. Having said that, in the years 2010 to 2012, there were quite a few bad slams bid that came home on very friendly distribution. On the other hand, some of the more desperate slams were the result of match situation, so the decision to bid slam was sometimes still sound.

3. One side bids Seven.

Grand failed seven times and succeeded on four. Even worse, on one occasion, the other side played the wrong small slam.

4. Both sides bid seven.

On ten occasions both sides bid and made seven. On one occasion both went down one, and one time one side made and the other did not. Including section 3, that is 25 making grands and 10 failing.

Conclusion

The decision to bid slam was right vastly more often than not, even when only one side bid slam. The poor decisions were usually those that involved NOT reaching slam. Overall, slam bidding appears to have improved over the period examined, but I will not look at this more till I have collated the other major world class events.

[jogs]

PhilKing, on 2013-February-26, 17:02, said:

OK. It took a few hours, but here you go. I chose the Spingold for my statistical study, since all the finals are available since 1996 with the exception of 2002. I have also included one semi-final where possible, so about 1500 deals all told. I will not regard the findings as definitive untill I have examined closer to 10K deals (which I will at some stage).

I collated four sets of statisitics:



2. Only one side bid slam.

More often, only one side reached slam. On broadly uncontested auctions, slam was successful 45 times and failed 21 times. On highly contested auctions, bidding slam was right twice, wrong three times, and had an unclear outcome twice.

This evidence utterly contradicts the myth of expert slam overbidding. They are not bidding enough. Having said that, in the years 2010 to 2012, there were quite a few bad slams bid that came home on very friendly distribution. On the other hand, some of the more desperate slams were the result of match situation, so the decision to bid slam was sometimes still sound.

3. One side bids Seven.

Grand failed seven times and succeeded on four. Even worse, on one occasion, the other side played the wrong small slam.



Conclusion

The decision to bid slam was right vastly more often than not, even when only one side bid slam. The poor decisions were usually those that involved NOT reaching slam. Overall, slam bidding appears to have improved over the period examined, but I will not look at this more till I have collated the other major world class events.

You're going too far back. That was then.
This is now.

Only interested in 2. and 3.

The world started bidding aggressively about 20 years ago.

Do the survey on your own team games.
Come back with results after 10 double session
swiss teams.

My survey was from the 2011 USBC and 2012 USBC.
Used only the semi-finals and finals matches.

[PhilKing]

jogs, on 2013-February-26, 17:34, said:

You're going too far back. That was then.
This is now.

Only interested in 2. and 3.

The world started bidding aggressively about 20 years ago.

Do the survey on your own team games.
Come back with results after 10 double session
swiss teams.

My survey was from the 2011 USBC and 2012 USBC.
Used only the semi-finals and finals matches.

Thanks Jogs. Thanks a bunch. Your knowledge of how the game has changed is clearly superior to mine, or maybe I did not explain plainly enough that slam bidding has been MORE accurate in the last few Spingolds, and my stats date back a mere 17 years. You are on "ignore" until I am worthy. Obviously a match where one team bid a load of grands off various winners (no offence) is far more statistically relevant, and not an outlier as I mistakenly thought.

And ROFL that you are only interested in 2. and 3. Do you not see the fallacy?

[Cyberyeti]

jogs, on 2013-February-26, 17:34, said:

You're going too far back. That was then.
This is now.

Only interested in 2. and 3.

The world started bidding aggressively about 20 years ago.

Do the survey on your own team games.
Come back with results after 10 double session
swiss teams.

My survey was from the 2011 USBC and 2012 USBC.
Used only the semi-finals and finals matches.

This is the most ungrateful response to a good player who helped you out with a response to the question you asked.

I've done this analysis on my own slam bidding, we VERY rarely bid non making slams or grands and the last three that failed were one misplayed not misbid, one you want to be in but got the required 5-0 trump break to beat it and one that went for 300 against their making slam, we usually bid more than our team mates but still not enough. The biggest loss in my slam bidding is where we investigate a slam, don't bid it and go off in 4N/5M/5m, this is almost impossible to catch by this sort of analysis.

In the Tollemache (inter county teams of 8 cross imped, one of the better competitions in the UK), our county (one of the smaller ones) almost invariably loses out on not completely obvious slam boards, we will bid the slam, both opps pairs will bid it and our other pair sitting in our direction will not bid it, this pattern has held true for many years.

[Zelandakh]

jogs, on 2013-February-26, 09:48, said:

Do a real study. Prove that I'm wrong.

Cyberyeti, on 2013-February-27, 03:36, said:

This is the most ungrateful response to a good player who helped you out with a response to the question you asked.

Come now Cyberyeti, you have been around online long enough to know that when someone writes something like the above quote, the very last thing they want is for someone actually to do a real study. My experience matches yours, that players tend to bid far too few slams and that this is an area where experts are considerably better. It is not that they are bidding too many slams so much as everyone else is not bidding them enough. And I suspect they are bidding them more often partly because someone noticed this and partly because methods are constantly improving to allow them to filter out the good slams from the bad more reliably.

Don't believe me? Then do a real study. Prove me wrong.

[gordontd]

jogs, on 2013-February-26, 17:34, said:

You're going too far back. That was then.
This is now.

Only interested in 2. and 3.

The world started bidding aggressively about 20 years ago.

1996 is not in the last 20 years?

[phoenix214]

@PhillKing

Did you also look at the hands were slams were unbid, but they have a good chance to make(Although i guess you didn`t do that)?
The interesting thing is if the are still bidding slams not aggressively enough

[lexlogan]

phoenix214, on 2013-February-23, 15:56, said:

... it pays off to put bid a slam that is on a finesse...

I'm having trouble determining what you meant here: "not bid" or "bid" or other?

[PhilKing]

phoenix214, on 2013-February-27, 09:10, said:

@PhillKing

Did you also look at the hands were slams were unbid, but they have a good chance to make(Although i guess you didn`t do that)?
The interesting thing is if the are still bidding slams not aggressively enough

No. But fortunately you already have enough data to suggest that holding back because of a bogus stat based on two tournaments is not the way to go!

I have files for hands from the big 5 tournaments since 2000 (Spingold, USBC, Vanderbilt, World Championships and European) where one side bid slam and one did not, but I have not searched for hands where 12 tricks were made.

I have enough on my plate processing those at the moment.