[MickyB]

Hypothetical scenario -

The declaring side give MI to the defence, contributing to a contract getting let through. Screens are in use, hence the MI not being corrected before the opening lead.

You estimate that, with the incorrect information, the defence were 60% to defeat the contract. With the correct information, they would have been 80% to defeat the contract.

What percentages of making and going off should be awarded? If it is not obvious, what's your methodology for determining this figure?

[CamHenry]

My immediate thought is 80% going off. The reasoning behind my methodology is to decide that choosing the unsuccessful line, which I have estimated will be selected 40% of the time given the MI, is an error but not Serious and Unrelated. It's probably not even Serious. I therefore rule that none of the damage was self-inflicted and that the most likely outcome, given correct information, is 80-20.

(As an aside: there *is* some damage under this ruling, relative to working it out at the table regardless of MI. That's life.)

[aguahombre]

CamHenry, on 2013-March-26, 08:44, said:

(As an aside: there *is* some damage under this ruling, relative to working it out at the table regardless of MI. That's life.)

Please explain. Isn't that part of the 80/20 estimate we started with?

[CamHenry]

aguahombre, on 2013-March-26, 09:07, said:

Please explain. Isn't that part of the 80/20 estimate we started with?

Not the way I meant it: I intended to say something along the lines of "if they'd got it right despite the MI, we'd rule no damage and call for the next case; however, some of the damage remains because we can't be certain they'd get it right even absent MI".

[blackshoe]

If I understand CamHenry, he's suggesting a weighted score of 80% down one and 20% making, because absent the MI the NOS would have failed to defeat the contract 20% of the time. My gut reaction is that the 20% is not "damage" in the sense that word is used in Law 12, but I don't have time right now to pursue it further.

[Vampyr]

I want to start with the 80/20 estimate without the MI, but add 40% (the estimate of the percentage of taking it off without the MI) of the remaining 20%. This compensates for the fact that the defenders didn't have the chance of 100% of defeating the contract, which they would have scored had they, in fact, defeated it.

But legally, 80/20 is probablythe only answer.

[Lanor Fow]

90/10
I was taught it's normal to wieght sympathetically to the NOS

[WellSpyder]

I'm confused by all this: 80/20 already sounds very generous to the NOS.

If I've understood the scenario correctly, and assuming we have estimated the percentages correctly, the defenders (the NOS) produced a defence that was among the 40% least favourable outcomes for them given the MI, since they were still 60% likely to defeat it. Now without the MI we estimate they are 80/20 to defeat it. So assuming they again produce a defence among the 40% least favourable outcomes for them then that means they will defeat the contract 20 times and let it through 20 times out of those 40 least favourable outcomes. So an unbiased weighting would be 50/50, or with some leaning towards the NOS then perhaps 60% defeating the contract and 40% letting it through.

[gordontd]

Unless we consider their defence to be wild, gambling, or a serious error unrelated to the infraction, what happened with the misinformation is irrelevant. What matters is what we think would have happened without it. And since we're rarely able to estimate with complete accuracy, we round up in favour of the NOS.

[WellSpyder]

gordontd, on 2013-March-26, 11:42, said:

Unless we consider their defence to be wild, gambling, or a serious error unrelated to the infraction, what happened with the misinformation is irrelevant. What matters is what we think would have happened without it. And since we're rarely able to estimate with complete accuracy, we round up in favour of the NOS.

Taken literally, that suggests some pretty harsh rulings. Let's suppose we estimate that they still had an 80% chance of defeating the contract with the MI, but without it they had an 85% chance of defeating it. (It was a pretty minor bit of MI, hence it doesn't change the odds very much.) Let's also suppose the defence wasn't wild or gambling. I don't think it can be unrelated to the infraction if we estimate the infraction altered the odds a bit, so it doesn't matter whether it was a serious error. Now if the NOS have let the contract through at the table you are going to give them a full 90% of defeating the contract, even though you only think the MI made perhaps 5% difference to their chances of beating it?

I guess what I'm really suggesting is that what happened with the MI may well not be irrelevant, since it will affect what you think would have happened without it.

[jallerton]

MickyB, on 2013-March-26, 08:36, said:

Hypothetical scenario -

The declaring side give MI to the defence, contributing to a contract getting let through. Screens are in use, hence the MI not being corrected before the opening lead.

You estimate that, with the incorrect information, the defence were 60% to defeat the contract. With the correct information, they would have been 80% to defeat the contract.

What percentages of making and going off should be awarded? If it is not obvious, what's your methodology for determining this figure?

I asked a very similar question a few months ago in this thread. There did not appear to be a consensus answer. Gordon's observation that "the Chairman of the WBF Laws Committee appears to take an approach at odds with the wording of the 2007 Laws" is interesting.

[Fluffy]

so 80-20 seems to be the consensous, now lets play a bit

if without MI defence was 60-40, same percentage, but different way to defeat, what now?

to make things worse, what if with correct information it was less likelly to be defeated? like 40-60? does it still sound likje 80-20 is fair?

[blackshoe]

That''s like asking if it's fair to rule MI in a revoke case. You've changed the scenario - generally that means changing the ruling.

[c_corgi]

Playing with the numbers can lead to some interesting results though, possibly changing the natural justice outcome if not the legal one. For instance:

A player is on lead and has been given MI which makes his choice of lead clear. With the MI he will have three 50-50 decisions to take, of which he will need to get at least 2 right to beat the contract, so he has a 50% chance of success overall. He got only 1 right and the contract made.

Case 1. Correcting the MI would have cleared up one of his three decisions so that he was 100% to get that one right. Without the MI he needs only to get at least one of 2 decisions right, so he had a 75% chance of defeating the contract. Does it matter what was the outcome of the decision that only existed because of the MI? Arguably if he got that one right anyway there was no damage. If he got that one wrong and exactly one other right, then arguably the without the MI the contract would be defeated 100% of the time given what happened at the table. But it is also arguable that you have to go back to the initial 75% chance from a legal perspective.

Case 2. Correcting the MI would have resulted in a different, but still automatic lead. The result of this is that all the key decisions would be taken by partner and the outcome would be truly independent of the decisions at the table. Partners chances of getting it right can be assigned various values leading to a similar situation to that discussed in jallerton's thread.

When applied to real hands, some of the arguments in case 1 would lead to complicated maths based on tenuous data. Should they be used anyway where possible?

[bluejak]

MickyB, on 2013-March-26, 08:36, said:

Hypothetical scenario -

The declaring side give MI to the defence, contributing to a contract getting let through. Screens are in use, hence the MI not being corrected before the opening lead.

You estimate that, with the incorrect information, the defence were 60% to defeat the contract. With the correct information, they would have been 80% to defeat the contract.

What percentages of making and going off should be awarded? If it is not obvious, what's your methodology for determining this figure?

Who are the offenders? Declaring side.

What might have happened without the infraction? The contract will go off four times in five.

How do you rule? 15% making, 85% going off, sympathetic weighting, you give the non-offenders a bit for luck.

WellSpyder, on 2013-March-26, 12:17, said:

Taken literally, that suggests some pretty harsh rulings. Let's suppose we estimate that they still had an 80% chance of defeating the contract with the MI, but without it they had an 85% chance of defeating it. (It was a pretty minor bit of MI, hence it doesn't change the odds very much.) Let's also suppose the defence wasn't wild or gambling. I don't think it can be unrelated to the infraction if we estimate the infraction altered the odds a bit, so it doesn't matter whether it was a serious error. Now if the NOS have let the contract through at the table you are going to give them a full 90% of defeating the contract, even though you only think the MI made perhaps 5% difference to their chances of beating it?

I guess what I'm really suggesting is that what happened with the MI may well not be irrelevant, since it will affect what you think would have happened without it.

Harsh rulings? Who cares? Let's just follow the Laws, ok?

[WellSpyder]

WellSpyder, on 2013-March-26, 12:17, said:

Taken literally, that suggests some pretty harsh rulings. Let's suppose we estimate that they still had an 80% chance of defeating the contract with the MI, but without it they had an 85% chance of defeating it. (It was a pretty minor bit of MI, hence it doesn't change the odds very much.) Let's also suppose the defence wasn't wild or gambling. I don't think it can be unrelated to the infraction if we estimate the infraction altered the odds a bit, so it doesn't matter whether it was a serious error. Now if the NOS have let the contract through at the table you are going to give them a full 90% of defeating the contract, even though you only think the MI made perhaps 5% difference to their chances of beating it?

I guess what I'm really suggesting is that what happened with the MI may well not be irrelevant, since it will affect what you think would have happened without it.

bluejak, on 2013-April-19, 08:35, said:

Harsh rulings? Who cares? Let's just follow the Laws, ok?

Yes, let's please follow the Laws. In order to do this, it is helpful for most of us to make sure we understand what the Laws are really saying.

If I can re-state my difficulty with this interpretation a different way, I suppose I am bothered that it appears to place under emphasis on the TD judging the percentages correctly. I can't find a quote immediately, but if I remember correctly no less a personage than bluejak has stated quite forcibly in defending weighted rulings that one of their advantages is that it doesn't really matter very much if the TD misjudges the percentages a bit, since it only makes a marginal difference to the scores of the participants. But that is decidedly not true if changing one's assessment of the likelihood of a particular occurrence from 80% to 85% changes the ruling from "no damage" to 90% of a favourable score that didn't occur at the table.

[campboy]

WellSpyder, on 2013-April-22, 11:14, said:

If I can re-state my difficulty with this interpretation a different way, I suppose I am bothered that it appears to place under emphasis on the TD judging the percentages correctly. I can't find a quote immediately, but if I remember correctly no less a personage than bluejak has stated quite forcibly in defending weighted rulings that one of their advantages is that it doesn't really matter very much if the TD misjudges the percentages a bit, since it only makes a marginal difference to the scores of the participants. But that is decidedly not true if changing one's assessment of the likelihood of a particular occurrence from 80% to 85% changes the ruling from "no damage" to 90% of a favourable score that didn't occur at the table.

The point is that when you are trying to work out whether the correct defence is more likely with correct information, say, you do not do this by estimating the two probabilities separately and then comparing them. You judge whether it is more likely first and think about percentages later. It is usually clear whether it is more likely, less likely, or there's no real difference. In the first case you adjust. The difference between thinking it has gone from 60% to 70% and thinking it has gone from 70% to 80% is not great.

[aguahombre]

campboy, on 2013-April-22, 14:06, said:

You judge whether it is more likely first and think about percentages later. It is usually clear whether it is more likely, less likely, or there's no real difference. In the first case you adjust.

That is my impression of weighted rulings. You judge what is more likely, and then instead of ruling that way, choose a wishy-washy result in case you are wrong.

Not you, in particular...the more general you.

[blackshoe]

You use a weighted ruling because there is some doubt as to what the actual outcome would have been. Because there is that doubt, you give the benefit of it to the NOS. Nothing "wishy-washy" about it.

[campboy]

aguahombre, on 2013-April-22, 14:36, said:

That is my impression of weighted rulings. You judge what is more likely, and then instead of ruling that way, choose a wishy-washy result in case you are wrong.

Not you, in particular...the more general you.

Well, a typical case is as follows. Declarer has to guess a queen, and should have no useful information. Because of MI, or because of a misleading pause or whatever, he thinks he knows where it is. We are sure that with the infraction he will always get it wrong, and you are sure that without the infraction he will sometimes, but not always, get it right. So we are sure that a weighted score is correct (except in the ACBL).