Hand Evaluation

[Trinidad]

BTW why would people be so resistant to a change in IMP scale (w.r.t. number of people on a team) when they are completely fine with a changing VP scale (w.r.t. number of boards)?

Beats me. I thought this was extremely simple. (I can understand that people find it difficult to understand how the IMP scale should be changed to make it like teams of four, but that is what mathematicians and engineers are for.)

 

Rik

[gnasher]

I suspect that nearly everyone playing in this competition for Cambridge UBC falls into either the "happily oblivious" or the "enlightened" (probably with varying degrees of annoyance).

Aren't they all too clever to fall into the "happily oblivious" camp?

[campboy]

Aren't they all too clever to fall into the "happily oblivious" camp?

That just affects the conclusion they come to once they stop to consider the merits of the scoring system, and some won't have done that. After all, most of the cantankerous people spend more time talking about cross-imps vs butlers or how the home team should move.

[bluejak]

The point is that this discussion got started because one of the players clearly did not like it.

 

In addition, there is the fact that people have already been thinking of a solution. After all, there must have been a reason why people were polled with the question whether they wanted the format changed from team of 8 to 2 teams of 4. I obviously don't have any hard evidence, since I was far from involved, but it seems to indicate that there must have been some kind of problem with the scoring. In general, people do not try to look for solutions if there isn't a problem.

I think this is a very unfair presumption. The reason that I polled them is that I realised that two teams-of-four would make the game what some people seem to call 'logical', ie more in line with playing teams-of-four, and because the scoring of the event [which was done by hand in those days] would be far simpler. Since I was the organiser [at the time] and the TD, it did not matter one brass farthing to me personally which way they decided really, and I would not let it affect me if it did.

 

Since no-one polled wanted a change I fail to see how you can presume the poll was because someone did.

 

PS Yes, this is analogous to the "how to score IMP pairs" question, but I think this is less bad than IMPing against a datum, which is completely barmy; I actively avoid playing in Butler-scored events unless required to.

Now I think that Butler has a lot to recommend it. At lower levels especially I think it is a better scoring method. Why? Because I think it better for the customers being more comprehensible to poor players.

 

BTW why would people be so resistant to a change in IMP scale (w.r.t. number of people on a team) when they are completely fine with a changing VP scale (w.r.t. number of boards)?

There are lots of different VP scales so no-one thinks of any one scale as the VP scale. but there is only one imp scale.

[Trinidad]

I think this is a very unfair presumption. The reason that I polled them is that I realised that two teams-of-four would make the game what some people seem to call 'logical', ie more in line with playing teams-of-four, and because the scoring of the event [which was done by hand in those days] would be far simpler. Since I was the organiser [at the time] and the TD, it did not matter one brass farthing to me personally which way they decided really, and I would not let it affect me if it did.

 

Since no-one polled wanted a change I fail to see how you can presume the poll was because someone did.

There is nothing unfair about my presumption. For starters, I was very clear that this was merely an indication.

 

If you "realised" that two teams of four would make the game more logical, you missed an important point of this discussion: It is complicated to come up with a single result when you split it in two teams of four matches. After all, you can match up:

- Table 1 and 2 in match 1 and table 3 and 4 in match 2

- Table 1 and 3 in match 1 and table 2 and 4 in match 2

- Table 1 and 4 in match 1 and table 2 and 3 in match 2

 

Each of these match-ups will lead to different results.

 

So there are two things you can do:

- Split up the team of 8 into two teams of 4 people. The consequence is that people won't play in a team of 8 anymore, but in a team of 4 whose result depends on that of another team of 4. That is principally different from team of 8.

- Calculate the results for the three different match-ups separately and add (or average) them. Now you have true teams of 8, with each pair in a team depending equally on each other pair. The only thing is that this is a lot harder to calculate than the method that uses an adjusted IMP scale.

 

And, as I explained earlier, it is pretty obvious that no one wanted to change if the only change that they can chose for is changing things for the worse.

 

Now I think that Butler has a lot to recommend it. At lower levels especially I think it is a better scoring method. Why? Because I think it better for the customers being more comprehensible to poor players.

Can you tell me why "first averaging results and then IMP" (Butler) is easier to comprehend than "first IMPing and than average results" (Cross-IMPs)? I would think the second is much easier to explain, since it is the correct order of doing things in every aspect of life: you average at the end, not at the beginning.

 

I think it is very hard to explain to poor players (and to good players) why the EW pairs on board 1 on average got an IMP more than the NS players (just to name only one oddity of Butler). What do you say when they come to you and tell that there must be a scoring error?

 

Rik

[Trinidad]

There are lots of different VP scales so no-one thinks of any one scale as the VP scale. but there is only one imp scale.

It is true: There is only one IMP scale. So why don't you use that one, instead of the "warped" one you are using?

 

I know, you don't realise that you are using a warped IMP scale, because you are fixed on numbers, rather than on underlying principles. I will try to explain. It is late at night here, which means that I am getting somewhat theatrical. I apologize, but please bear with me. At the end of the theater you may understand.

 

You know that there is only one IMP scale. But did you know that there is also only one VP scale. (?!?) Yes, indeed, there is only one VP scale.

I don't know what it is, but this VP scale always "bends" at the exact right places, whether you play 8 or 32 boards. I know, the numbers are different, but the bending of the scale is always at the same place: Whether you win 16-14 in VP at the end of 8 boards or after 32 boards, in both cases you will feel that it could have gone either way. And if you win 20-10, you feel that you had a solid win. Whenever you win 25-3, you felt that you were blitzing them. The VP scale expresses achievements in numbers. And it does so always in the same way. 4, 8, 12, 24 or 32 boards: it doesn't matter. The VP scale always shows how much stronger (or weaker) you were than the opponents. It is mystical, no, no, ...magical.. how this can be achieved.

 

If you compare the VP table for 8 boards to the VP table for 32 boards, you will notice something interesting: The IMP differences of the 8 board table are half of the IMP differences of the 32 board table. What a coincidence! Or might it be deliberate? 8/32=1/4, and the square root of 1/4 equals 1/2! That is too much of a coincidence.

Wait a minute! There is only one VP scale! All VP scales are mathematically created from one universal, invisible Master VP scale. Now where did I hear that concept before?

 

'And the Master VP scale said: "Let us make VP scales in our image, in our likeness, so that they may rule over the palookas in the clubs and the pros in the tournaments, over the rabbits and the hogs, and over all the players that move for the round."'

I believe that the one IMP scale is just as Almighty as the one VP scale.

 

Rik

[bluejak]

There is nothing unfair about my presumption. For starters, I was very clear that this was merely an indication.

 

If you "realised" that two teams of four would make the game more logical, you missed an important point of this discussion: It is complicated to come up with a single result when you split it in two teams of four matches. After all, you can match up:

- Table 1 and 2 in match 1 and table 3 and 4 in match 2

- Table 1 and 3 in match 1 and table 2 and 4 in match 2

- Table 1 and 4 in match 1 and table 2 and 3 in match 2

 

Each of these match-ups will lead to different results.

 

So there are two things you can do:

- Split up the team of 8 into two teams of 4 people. The consequence is that people won't play in a team of 8 anymore, but in a team of 4 whose result depends on that of another team of 4. That is principally different from team of 8.

- Calculate the results for the three different match-ups separately and add (or average) them. Now you have true teams of 8, with each pair in a team depending equally on each other pair. The only thing is that this is a lot harder to calculate than the method that uses an adjusted IMP scale.

 

And, as I explained earlier, it is pretty obvious that no one wanted to change if the only change that they can chose for is changing things for the worse.

Your presumptions are getting more and more extreme and teetering on the edge of being rather rude. Of course there are several ways you can do it. When I polled them I gave them an easy working alternative: I did not just tell them a load of confusing rubbish. They just preferred the present method. Why is that so hard to understand?

 

Can you tell me why "first averaging results and then IMP" (Butler) is easier to comprehend than "first IMPing and than average results" (Cross-IMPs)? I would think the second is much easier to explain, since it is the correct order of doing things in every aspect of life: you average at the end, not at the beginning.

The concept of a datum is one people find easy to understand. Cross-imps has no datum. Easy peasy.

 

I think it is very hard to explain to poor players (and to good players) why the EW pairs on board 1 on average got an IMP more than the NS players (just to name only one oddity of Butler). What do you say when they come to you and tell that there must be a scoring error?

Poor players do not worry about the oddity of Butler once they understand the principle, you get a datum, you imp against that.

 

It is true: There is only one IMP scale. So why don't you use that one, instead of the "warped" one you are using?

 

I know, you don't realise that you are using a warped IMP scale, because you are fixed on numbers, rather than on underlying principles. I will try to explain. It is late at night here, which means that I am getting somewhat theatrical. I apologize, but please bear with me. At the end of the theater you may understand.

 

You know that there is only one IMP scale. But did you know that there is also only one VP scale. (?!?) Yes, indeed, there is only one VP scale.

I don't know what it is, but this VP scale always "bends" at the exact right places, whether you play 8 or 32 boards. I know, the numbers are different, but the bending of the scale is always at the same place: Whether you win 16-14 in VP at the end of 8 boards or after 32 boards, in both cases you will feel that it could have gone either way. And if you win 20-10, you feel that you had a solid win. Whenever you win 25-3, you felt that you were blitzing them. The VP scale expresses achievements in numbers. And it does so always in the same way. 4, 8, 12, 24 or 32 boards: it doesn't matter. The VP scale always shows how much stronger (or weaker) you were than the opponents. It is mystical, no, no, ...magical.. how this can be achieved.

 

If you compare the VP table for 8 boards to the VP table for 32 boards, you will notice something interesting: The IMP differences of the 8 board table are half of the IMP differences of the 32 board table. What a coincidence! Or might it be deliberate? 8/32=1/4, and the square root of 1/4 equals 1/2! That is too much of a coincidence.

Wait a minute! There is only one VP scale! All VP scales are mathematically created from one universal, invisible Master VP scale. Now where did I hear that concept before?

 

 

I believe that the one IMP scale is just as Almighty as the one VP scale.

Now you are talking complete rubbish. Of course there is not only one VP scale. Please explain how my 17-3 win in Swiss Pairs is identical to my 8-4 win in my local league. And don't think that your method of blinding me with numbers proves anything: it doesn't.

 

I do think one of the problems is that you do not realise that simple concepts can be explained simply.

[gordontd]

Poor players do not worry about the oddity of Butler once they understand the principle, you get a datum, you imp against that.

Sure they wonder: why do we discard some scores, how many scores are discarded? And then less inexperienced players might wonder how it is determined the number of scores that are discarded, why they can't find a regulation to explain this, what happens to scores that fall between the IMP scales, and why an improved score on one board might make their overall score worse.

 

By contrast, I have never known players have difficulty understanding Cross-IMPs when it is explained properly to them.

[WellSpyder]

FWIW, I feel strongly that Cross-imps are better than Butler imps, and suggest changing from Butlers whenever the opportunity arises. But there is usually very little enthusiasm for this since everyone is used to Butlers and most don't care about the distortions involved.

 

As far as the main topic of conversation here is concerned, I play in two different teams of 8 leagues. The Midlands inter-county league, unlike the Eastern counties one that started this discussion, is scored as 2 teams of 4. It still feels very much like a teams of 8 match, though, since you end up playing all 4 pairs in the opposing team, and of course the scores of both teams of 4 are added together at the end. Within our county, on the other hand, we run a large teams of 8 league (around 40 teams in 5 divisions) which is scored by adding all 4 scores together and imping using the standard teams of 4 scale. (I also tend to play once a year in a multiple teams of 8 inter-county event that is scored by imping with both pairs sitting the other way. This uses the standard teams of 4 imp scale, but needs a special VP scale since there are 4 imps scores on every board.)

 

Having experience of all these, I think the cross-imp form of teams of 8 is probably the purest way to score. But I much prefer actually playing in the league that simply scores as 2 teams of 4, because it is so simple! The players can very quickly score up as normal and know how well they have done, whereas both the other forms of scoring take significantly longer, and are probably quicker to do on a computer than by hand.

[mjj29]

The concept of a datum is one people find easy to understand. Cross-imps has no datum. Easy peasy.

Really? I don't understand the concept of a datum - I have no idea why you would consider the mean of the available scores a reasonable thing to imp against or why it's reasonable to discard that number of outliers. I don't understand why it's ever reasonable to imp against a score that noone (including the computer) actually got on that board.

 

Cross-imps, on the other hand, are both very easy to explain to people ('you imp against everyone and take the average') and seem much more sensible when you consider them in any detail.

 

Poor players do not worry about the oddity of Butler once they understand the principle, you get a datum, you imp against that.

 

Surely poor players don't worry about the scoring at all though and would be happy with any method of scoring. At best they want to know 'is it IMPs or pairs', although most of them don't change their play either way, it just gives them a different set of excuses for bidding failing games. Why, therefore, should we give them a statistically bogus method of scoring, rather than a reasonable one?

[WellSpyder]

Surely poor players don't worry about the scoring at all though and would be happy with any method of scoring. At best they want to know 'is it IMPs or pairs', although most of them don't change their play either way...

Indeed. We play Butler pairs once a month at my club, but the Bridgemates still display match point percentages when scores are entered. I'm quite struck by how many people take a serious interest in whether they have scored, say, 50% or 60% on a hand, even though this has virtually nothing to do with their imp score on the hand.

[barmar]

Really? I don't understand the concept of a datum - I have no idea why you would consider the mean of the available scores a reasonable thing to imp against or why it's reasonable to discard that number of outliers. I don't understand why it's ever reasonable to imp against a score that noone (including the computer) actually got on that board.

In Butler scoring, you treat "the field" as the opposing team. So to get their score, you average all the results. The metaphor would work better if you excluded your own score when computing the datum to IMP against, but that would also negate much of the calculation benefit of using the datum.

 

But as I mentioned earlier, I think the real reason for Butler scoring was because it was developed before computer scoring. Calculating cross-IMPs takes N times as along as Butlers, where N is the number of tables. But once computers took over the job of scoring, it's mainly inertia that keeps it around. Most players don't really think about the mathematics of it, they just like what they're used to.

[mycroft]

I would have thought that teams-of-8 were, actually, "score all 4 matches and combine/average the IMPs" - computers should be able to do that straight up, right?

 

I don't see a problem with any scoring method, frankly, but the IMP table *is* designed for head-to-head results, rather than any combination, be it datum or "add the scores and IMP the difference". It doesn't matter, however, as long as it's known in advance, and people can play to it.

[Vampyr]

FWIW, I feel strongly that Cross-imps are better than Butler imps, and suggest changing from Butlers whenever the opportunity arises. But there is usually very little enthusiasm for this since everyone is used to Butlers and most don't care about the distortions involved.

 

Cross-imping is now the norm in my part of the world, which is not too far from your part of the world.

[Trinidad]

In Butler scoring, you treat "the field" as the opposing team. So to get their score, you average all the results. The metaphor would work better if you excluded your own score when computing the datum to IMP against, but that would also negate much of the calculation benefit of using the datum.

 

But as I mentioned earlier, I think the real reason for Butler scoring was because it was developed before computer scoring. Calculating cross-IMPs takes N times as along as Butlers, where N is the number of tables. But once computers took over the job of scoring, it's mainly inertia that keeps it around. Most players don't really think about the mathematics of it, they just like what they're used to.

The point of Butler is that you do not treat the field as the opposing team. Instead, you create some weird average as "the opposing team".

 

Would anybody get the idea of scoring "Board a Match Pairs"? (All pairs are scored against the datum, scoring 1 for a win, 0 for a loss and 1/2 for a tie.) Of course not. It is obvious that you get a better way of seeing who is best if you compare against the whole field, rather than against some average. For IMPs, this is not different. You should use the whole field as the opposing team, instead of only the "average" of the field. And then you get to Cross-IMPs.

 

Rik

[bluejak]

Really? I don't understand the concept of a datum - I have no idea why you would consider the mean of the available scores a reasonable thing to imp against or why it's reasonable to discard that number of outliers. I don't understand why it's ever reasonable to imp against a score that noone (including the computer) actually got on that board.

That is because you are not typical. Poor players find imps much much easier to understand where it is their score imped against another score: the datum.

 

Cross-imps, on the other hand, are both very easy to explain to people ('you imp against everyone and take the average') and seem much more sensible when you consider them in any detail.

Far more difficult, far less comprehensible. Not to you, but I am not talking about you.

 

Surely poor players don't worry about the scoring at all though and would be happy with any method of scoring. At best they want to know 'is it IMPs or pairs', although most of them don't change their play either way, it just gives them a different set of excuses for bidding failing games. Why, therefore, should we give them a statistically bogus method of scoring, rather than a reasonable one?

First of all, it is not statistically bogus, so stop trying to sneak such comments in. It is statistically fine. What you mean is that you and good players believe cross-imps is better, and can produce a justification.

 

Secondly, to repeat, poor players understand imps as a method of taking their score, another score, and there you are: imps.

[barmar]

The point of Butler is that you do not treat the field as the opposing team. Instead, you create some weird average as "the opposing team".

I don't understand this response. If you want to treat the field as the opposing team, and IMP against it, you need a single score. How do you turn a dozen scores into a single score? Averaging is something most people think they understand, it's used in all walks of life. It's not always appropriate (have you ever met a family with 2.4 kids?), but it's ubiquitous.

[mycroft]

Well, except for the fact that those 2.4 kids are based on all families except the 100 000 with the most and the 100 000 with the least number of kids. Which might, just, skew the number a little.

 

I've found that Butler makes sense to the people who have had Butlered IMPs explained to them when they first played it, and have played it ever since; and cross-IMPs make sense to the people who ask me 15 minutes to gametime, the session after, "why did I get scores like -1.85 and 3.62?" Usually if one of those asks the long-timers, they get the explanation of how Butler works; if I hear that discussion, I try to move in to correct it, because "we don't do that any more".

 

Fortunately, that's becoming less common as we haven't had a Butlered IMP pairs game in this area for 8 or 9 years.

[campboy]

First of all, it is not statistically bogus, so stop trying to sneak such comments in. It is statistically fine. What you mean is that you and good players believe cross-imps is better, and can produce a justification.

I do not claim to be a "good player", but I am a good mathematician. What we mean by "statistically bogus" is Butlering has very poor statistical properties, such as imbalance of NS and EW scores, high sensitivity to changes in distant scores, distortion of the IMP scale and discretisation effects. What is your justification for saying it is "statistically fine"?

[bluejak]

Same for everyone.

[PeterAlan]

Same for everyone.

So's the same score on every board for everyone, N! points for the winner (however defined) of Board N, or any other idiotic scoring system one could dream up that applied equally to all participants. I think you need a better reason.

[c_corgi]

If, as seems both reasonable and inevitable, we persist with using IMPs for anything other than long head to head matches, shouldn't we just accept that the results will be less "pure"?

[Trinidad]

If, as seems both reasonable and inevitable, we persist with using IMPs for anything other than long head to head matches, shouldn't we just accept that the results will be less "pure"?

Cross-IMPs are certainly not less "pure" than head to head team of four IMP scoring. As a matter of fact, Cross-IMPs are much "purer" than head to head teams of four because the data set is much larger.

 

So, there is no argument against using IMP scoring for pairs competitions. The only point is that you should use the mathematically correct method to do it. Cross-IMPs are mathematically correct and Butler is mathematically awful.

 

Rik

[bluejak]

So's the same score on every board for everyone, N! points for the winner (however defined) of Board N, or any other idiotic scoring system one could dream up that applied equally to all participants. I think you need a better reason.

I have already given perfectly good reasons why customer satisfaction is important in such decisions, rather than mathematical irrelevancies. Comparing with something people will hate hardly seems relevant. If that is your best argument, which need I bother?

[pran]

I have already given perfectly good reasons why customer satisfaction is important in such decisions, rather than mathematical irrelevancies. Comparing with something people will hate hardly seems relevant. If that is your best argument, which need I bother?

I would expect (assume) that those who "hate" Cross IMPs do so because of ignorance and "fear of the unknown". This is no argument against a "better" scoring method.

 

Count me in with those who prefer Cross IMPs for Butler, except that I favour "Normalized" Cross IMPs where the total amount of IMPs on a board is divided by the number of comparisons on that board for easier recognition of the results.