Split/weighted score, teams

[szgyula]

Dear All,

 

I have a long argument with the national authorities and we seem to disagree fundamentally: How to calculate a split score with weighting in TEAMS?

 

To give an example: 32 boards, teams. Boards 1-31 are all 0IMP. Board 32 is W4S in both rooms. In closed room it goes down 1 for -100. In the open room there is MI and as a result West makes for 620. The TD makes two rulings: 1. Without the MI it would be down 1. 2. There was SEWoG by the NOS, which is responsible for 50% of the damage.

 

There are four proposals to calculate the score:

 

1. Do it in total points: OS gets -100 in the open room. The SEWoG was worth 720 points, 50% of that is 360, i.e. the board result is 260 for the OS, difference is 360 points, 8IMP, 11.67-8.33VP for the OS.

 

2. Do it in IMP: OS gets 0IMP for the board (-100 points in both rooms). The -620 vs. +100 is -720 points, -12IMP. The NOS gets half of this, -6IMP for SEWoG. Board result is 0:-6IMP, teams result is 11.27-8.73VP for the OS.

 

3. Do it with mixed IMP+VP: The 50% SEWoG is calculated as above, i.e. -6IMP. Now we do the split score in VPs. The OS gets 10VP (i.e. ignoring the SEWoG correction) but the NOS gets 8.73VP as above. Thus, 10-8.73VP.

 

4. Everything is done in VP: OS gets 10VP. The NOS, without the SEWoG would have scored 10VP. With the SEWoG, the NOS would have scored 7.68VP (-12IMP, 32 boards). Thus, the error was worth 2.42VP. Half of it is 1.21VP, thus, teams result is 10-8.79VP.

 

Law 86D says

 

"In team play when the Director awards an adjusted score (excluding any award that ensues from application of Law 6D2), and a result has been obtained* between the same contestants at another table, the Director may

assign an adjusted score in IMPs or total points (and should do so when that result appears favourable to the non-offending side)."

 

This unfortunately includes "may", i.e. one can interpret the two choices as suggestions that do not exclude other methods.

 

White book 4.1.1.4 says: "This is done by converting each score to match points or IMPs and then applying the weighting." Example (b) supports this.

 

White book 4.1.3.1 seems to cover exactly this topic and seems to support option 2. A small step is missing from the example. The example says OS gets 0IMP (in that example), NOS gets -4IMP.Does this imply that the board result is 0:-4IMP, i.e. -4IMP for the OS and the VP result will still add up to 20?

[WellSpyder]

I don't think there is any reason why VPs should add up to 20. I believe the procedure set out in the White Book means that the OS gets the VPS associated with their imp score (ie 10 VPs for 0 imps in your example) while the NOS get the VPs associated with their imp score (8.73 VPs for -6 imps according to your calculations).

[gordontd]

Law 86D says

 

"In team play when the Director awards an adjusted score (excluding any award that ensues from application of Law 6D2), and a result has been obtained* between the same contestants at another table, the Director may assign an adjusted score in IMPs or total points (and should do so when that result appears favourable to the non-offending side)."

 

This unfortunately includes "may", i.e. one can interpret the two choices as suggestions that do not exclude other methods.

I don't think so. The option is to assign or not, but if you do assign it is in IMPs or total points, not some other method.

 

White book 4.1.1.4 says: "This is done by converting each score to match points or IMPs and then applying the weighting." Example (b) supports this.

 

White book 4.1.3.1 seems to cover exactly this topic and seems to support option 2. A small step is missing from the example. The example says OS gets 0IMP (in that example), NOS gets -4IMP.Does this imply that the board result is 0:-4IMP, i.e. -4IMP for the OS and the VP result will still add up to 20?

When you deny redress it is only for the NOS, so the scores should not balance. In this case (ie 0 -4 IMPs, not your original example) the scores should be 10.00 - 9.14

[RMB1]

To give an example: 32 boards, teams. Boards 1-31 are all 0IMP. Board 32 is W4S in both rooms. In closed room it goes down 1 for -100. In the open room there is MI and as a result West makes for 620. The TD makes two rulings: 1. Without the MI it would be down 1. 2. There was SEWoG by the NOS, which is responsible for 50% of the damage.

 

We would not normally rule on a SEWoG case by declaring the proportion of the damage is due to the erroneous action - instead we would say that if there had been no SEWoG then NOS would have obtained a different/better score (possibly weighted) and say that the damage due to the SEWoG was the difference between the score at the table and the score without the SEWoG.

[szgyula]

We would not normally rule on a SEWoG case by declaring the proportion of the damage is due to the erroneous action - instead we would say that if there had been no SEWoG then NOS would have obtained a different/better score (possibly weighted) and say that the damage due to the SEWoG was the difference between the score at the table and the score without the SEWoG.

 

OK but how do you calculate the "difference"? In total points? IMP? VP? What do you correct with this difference? Total points for the board? IMPs for the board? VP for the teams event? Final ranking for the whole tournament?

 

The White Book has an example calculation for a split score (4.1.3.1) that is done in IMP for teams. There is no conclusion as to what that implies for the VP result. The WB also has examples for VP results that do not add up to 20VP but both examples given are AVE+/AVE+ cases. One is TD error that can not be rectified, the other is an unplayable board where neither side is at fault.

[RMB1]

OK but how do you calculate the "difference"? In total points? IMP? VP? What do you correct with this difference? Total points for the board? IMPs for the board? VP for the teams event? Final ranking for the whole tournament?

 

The White Book has an example calculation for a split score (4.1.3.1) that is done in IMP for teams. There is no conclusion as to what that implies for the VP result. The WB also has examples for VP results that do not add up to 20VP but both examples given are AVE+/AVE+ cases. One is TD error that can not be rectified, the other is an unplayable board where neither side is at fault.

 

We calculate the difference in IMPs.

 

The final calculation will result in non-balancing IMP scores, and we calculate the VP separately for the two sides, resulting in non-balancing VP scores.

[nige1]

SEWOG law + Weighted ruling = unnecessary quagmire :(

[szgyula]

We calculate the difference in IMPs.

 

The final calculation will result in non-balancing IMP scores, and we calculate the VP separately for the two sides, resulting in non-balancing VP scores.

 

And now the 1000 dollar question: How to do weighting? In VP or IMP? The IMP-VP function is not linear, thus, it does matter...

[gordontd]

And now the 1000 dollar question: How to do weighting? In VP or IMP? The IMP-VP function is not linear, thus, it does matter...

Haven't you already had this answered, by me, by the White Book and by Robin?

[szgyula]

Haven't you already had this answered, by me, by the White Book and by Robin?

Not clearly enough for me (my fault probably). Let me retry to phrase my question. Hwo to calculculate the self inflicted damage and how to calculate the weighted result? Lets ignore the OS for a second (they get the adjusted score, not correction for SEWoG). Table result is what happened (-620 for NOS), adjusted is what would have happened without infraction (+100 for NOS). Other room is always -100 for NOS team.

 

NOS calculation #1, with SEWoG, for the NOS: table result vs other room. -620-100=720.

 

NOS calculation, without SEWoG, for the NOS: adjusted result vs. other room, +100-100=0.

 

Now what do you weight 50%:50%?

 

1. 720 and 0 total points for 360 total points (SEWoG difference in total points, weighted). In this case you can actually do this without rounding issues. Result is -8IMP, end result is 8.33VP.

2. The corresponding IMPs: 12 IMP (720 total points) vs. 0IMP, resulting in -6IMP for NOS (SEWoG difference in IMP, weighted). End result is 8.73VP.

3. The corresponding VPs: 7.58VP (12IMP) vs. 10VP (0IMP), resulting in 8.79VP (SEWoG difference in VP, weighted).

 

I do not get the 9.13VP result.

[gordontd]

Not clearly enough for me (my fault probably). Let me retry to phrase my question. Hwo to calculculate the self inflicted damage and how to calculate the weighted result? Lets ignore the OS for a second (they get the adjusted score, not correction for SEWoG). Table result is what happened (-620 for NOS), adjusted is what would have happened without infraction (+100 for NOS). Other room is always -100 for NOS team.

 

NOS calculation #1, with SEWoG, for the NOS: table result vs other room. -620-100=720.

 

NOS calculation, without SEWoG, for the NOS: adjusted result vs. other room, +100-100=0.

 

Now what do you weight 50%:50%?

 

1. 720 and 0 total points for 360 total points (SEWoG difference in total points, weighted). In this case you can actually do this without rounding issues. Result is -8IMP, end result is 8.33VP.

2. The corresponding IMPs: 12 IMP (720 total points) vs. 0IMP, resulting in -6IMP for NOS (SEWoG difference in IMP, weighted). End result is 8.73VP.

3. The corresponding VPs: 7.58VP (12IMP) vs. 10VP (0IMP), resulting in 8.79VP (SEWoG difference in VP, weighted).

You weight the IMPs, giving 8.73 VPs

I do not get the 9.13VP result.

That's because you gave two examples, one with -6 IMPs and one with -4 IMPs. I was answering the -4 IMPs question, which does come to 9.13 VPs for a 32 board match.

[sanst]

And now the 1000 dollar question: How to do weighting? In VP or IMP? The IMP-VP function is not linear, thus, it does matter...

Not in VP's, since these are not in the Laws. IMNSHO you should stick to IMP's. What advantage offer VP's?

[szgyula]

Not in VP's, since these are not in the Laws. IMNSHO you should stick to IMP's. What advantage offer VP's?

OK. I bought that: There is no VP in the laws, thus, everything is in IMPs. Split score and weighted score. Board result is 0IMP for OS, -6IMP for the NOS. As all other boards are 0IMP, this is the final result. Now the only remaining question: What is the definition of VP? How to calculate it?

 

There is no country specific regulation, we simply refer to WBF. WBF has this statement:

 

"IMP margin translates to a specific VP award"

 

Notice "margin". It can be interpreted as "IMP margin=difference in IMP", in which case there is a split result in IMP but not in VP. Thus, I would like to see a definite statement as to how VP should be calculated. I can (extreme, I know) argue that "IMP translates to VP" would allow split VP results. The use of "margin" there explicitly forces us to calculate the IMP difference, no matter how the IMPs are calculated. Without split score, IMP and IMP margin are identical. "Margin" is there for a reason....

[campboy]

Without split score, IMP and IMP margin are identical. "Margin" is there for a reason....

No, they aren't. Traditionally, the team that wins a board is awarded some IMPs as defined in Law 78B, and the other team gets nothing; then the result is determined by seeing which team got more IMPs. This is why 78B only lists positive scores. So "IMPs" would just be the IMPs won; "IMP margin" is the IMPs won minus the IMPs conceded. Normally, your IMP margin is just the negative of your opponents' IMP margin (because your IMPs won on a board = their IMPs conceded, and vice versa), but when a score is split this will not be so.

[gordontd]

OK. I bought that: There is no VP in the laws, thus, everything is in IMPs. Split score and weighted score. Board result is 0IMP for OS, -6IMP for the NOS. As all other boards are 0IMP, this is the final result. Now the only remaining question: What is the definition of VP? How to calculate it?

 

There is no country specific regulation, we simply refer to WBF. WBF has this statement:

 

"IMP margin translates to a specific VP award"

 

Notice "margin". It can be interpreted as "IMP margin=difference in IMP", in which case there is a split result in IMP but not in VP. Thus, I would like to see a definite statement as to how VP should be calculated. I can (extreme, I know) argue that "IMP translates to VP" would allow split VP results. The use of "margin" there explicitly forces us to calculate the IMP difference, no matter how the IMPs are calculated. Without split score, IMP and IMP margin are identical. "Margin" is there for a reason....

Is all of this to any purpose?

[szgyula]

Is all of this to any purpose?

Yes. Split score (whatever reason). 0IMP for one side, -6IMP for the other side. What is the result in VP assuming 32 boards? 11.27-8.73 or 10-8.73? What is the reason? 11.27-8.73 is basically the IMP margin converted to VP. 10-8.73 is the two versions, 0IMP and -6IMP both converted to VP and keeping only half of those numbers.

 

One more quote "If team A wins V Victory Points, then its opponent, team B, wins (20−V) Victory Points."

 

The long term goal is to clarify the rules so we do not have these arguments over and over.

[RMB1]

One more quote "If team A wins V Victory Points, then its opponent, team B, wins (20−V) Victory Points."

 

Whose quote is that? It is not a rule in some jurisdictions.

 

If it is a rule in your jurisdiction, there needs to be a rule for converting non-balancing IMPs to reciprocal VPs.

You could extend the mechanism in Law 86B to apply to victory-pointed teams, not just knockout.

[WellSpyder]

The long term goal is to clarify the rules so we do not have these arguments over and over.

The rules have been clarified as far as the rest of the world is concerned, as has been explained by more than one person above. THERE IS NO NEED FOR VP SCORES TO ADD UP TO 20.

 

As RMB1 implies, if your part of the world wants to do this differently, then you probably need your own regulations about how you do this since other people's regulations are not designed with a 20VP constraint in mind.

[gordontd]

Yes. Split score (whatever reason). 0IMP for one side, -6IMP for the other side. What is the result in VP assuming 32 boards? 11.27-8.73 or 10-8.73? What is the reason? 11.27-8.73 is basically the IMP margin converted to VP. 10-8.73 is the two versions, 0IMP and -6IMP both converted to VP and keeping only half of those numbers.

 

One more quote "If team A wins V Victory Points, then its opponent, team B, wins (20−V) Victory Points."

 

The long term goal is to clarify the rules so we do not have these arguments over and over.

So are you responsible for these regulations and looking for input from other countries? Or do you just not like the way your country implements them?

[szgyula]

I think we are overcomplicating this. I am just looking for some document, law, etc. in WBF territory that explains how to convert IMP to VP. "If team A wins V Victory Points, then its opponent, team B, wins (20−V) Victory Points" is from a 2013 technical paper by WBF. This is the closest I saw so far to an actual description of the calculation. It is my fault, probably but I looked hard. Someone may be able to point to the relevant WBF regulation.

 

All I ask is a simple quote from anything that explains how to convert IMP to VP that can be applied. So far I saw "VP does not have to add up to 20". There is a huge leap from this to the actual method to be used.

 

The purpose is to find a the definite answer and make it more visible, make it easier to find. The short term goal is to update the national regulations (CoC) on may points (unrelated ones) and put in an explicit rule as to how VP is calculated.

[WellSpyder]

All I ask is a simple quote from anything that explains how to convert IMP to VP that can be applied. So far I saw "VP does not have to add up to 20". There is a huge leap from this to the actual method to be used.

But the regulations already tell you what VPs are awarded for a given net imp score. So just apply this for each team, and there is your "actual method".

[barmar]

A typical VP chart has a row like this:

 

IMPS VPs

5-7 13-7

 

The ways this is shown is for the normal case where VPs balance. But it can also be read as: +5 through +7 IMPs gets 13 VP, -5 through -7 IMPs gets 7 VPs. When dealing with split scores, you would use the latter method.

[szgyula]

A typical VP chart has a row like this:

 

IMPS VPs

5-7 13-7

 

The ways this is shown is for the normal case where VPs balance. But it can also be read as: +5 through +7 IMPs gets 13 VP, -5 through -7 IMPs gets 7 VPs. When dealing with split scores, you would use the latter method.

This question was more along the lines of "what is the order of differnt operations"? You have "split score", you have "weighting" and you have "IMP to VP". Apparently the correct order is:

 

1. Weighting

2. IMP to VP

3. Split score

 

To me this appears to be a "case law", i.e. somebody started to do it this way and we stick to that lacking any compelling reason to do something different, e.g. to calculate the weighting in VP.

[mycroft]

If we have a split and weighted score, we IMP and convert to VP all splits and alternative scores, and apply the assigned weighting.

 

For instance (totally ignoring the hand in question):

 

All other boards of the match, Team A is +6 IMPs. Scoring is on the 6-8 board, ACBL 20 point VP scale (because that's the one I know).

 

Board 7, in the open room, N/S A is 4S+2, +680.

In the closed room, the table result is E/W A 5Dx-2, N/S +500.

However, there's a MI ruling. With the correct information, N/S are never sitting, and we think finding the slam is an outside chance, but not likely. The TD decides to assign:

30% N/S B 6S=, +1430;

70% N/S B 5S+1, +680.

However, again, it is deemed that South doubled as a Gambling Action, "knowing" that she'd been given MI, and counting on the TD to recover to however many spades makes if she didn't take 5♦ for enough. So, E/W get the assigned score, and N/S get something. I'm not an expert at this (by any stretch!), so I'm sure my suggested assigned score is unreasonable, but let's say relief for that part of the damage that was not self-inflicted is deemed to be:

30% N/S B 6S=, +1430;

70% E/W A 5Dx-2, N/S +500.

 

So:

E/W get a match result of: 30% of -7 (+6 -13 for the slam swing) and 70% of +6: 30% of 7 + 70% of 13 = 2.1 + 9.1 = 11.2 VPs.

N/s get a match result of: 30% of +7 and 70% of -11 = 30% of 13 + 70% of 5 = 3.9 + 3.5 = 7.4 VPs.

Yes, the scores don't add up to 20. This isn't a problem, both sides were "offending".

[szgyula]

So:

E/W get a match result of: 30% of -7 (+6 -13 for the slam swing) and 70% of +6: 30% of 7 + 70% of 13 = 2.1 + 9.1 = 11.2 VPs.

N/s get a match result of: 30% of +7 and 70% of -11 = 30% of 13 + 70% of 5 = 3.9 + 3.5 = 7.4 VPs.

Yes, the scores don't add up to 20. This isn't a problem, both sides were "offending".

 

Here you did the weighting in IMP. You could have done it in VP. For the discrete, 30VP scale that would be very difficult of course. For the new, 20VP scale that is trivial. You also reduce the rounding errors. If you weight in IMP, you can introduce 0.5IMP errors (the 20VP scale needs integer IMP results). If you weight in VP, you introduce errors at most 0.005VP. This is already "accepted" as there are 0.01VP corrections in the formula to make the curve behave nicely: As you move away from a tie, each IMP step must result in a non increasing VP step, even after rounding to 0.01VP. This requires small corrections...

 

I am not saying this is better. I am not saying it should be done this way. I am just saying that this is more like case law than written law. Historically weighting is done in IMP, full stop.

 

Rounding is also an issue that must be clearly regulated.