IMP scoring

[Deanrover]

I'd like to see a form of IMP scoring that I am sure has an official name, maybe Butler, not sure of that.

 

When comparing your score in order to give the IMP result, I'd lke to see the "highest" and "lowest" scores removed in order to give an "adjusted mean". I think it would give a more accurate representation of the hand, and would remove from the equation some of the more eccentric results we see. I appreciate that over the long run, you are as likely to be lucky as unlucky in your comparisons, but this would be beneficial in the short run, thus ideal for tourneys (depending on the size of which more than 2 boards would be removed).

[1eyedjack]

This has been discussed a few times in these forums. I for one prefer the existing method.

 

Have a look at

 

http://bridgebase.lunarpages.com/~bridge2/...=2835&hl=Butler

 

to name just one thread (I only picked that one because I had some input to it).

[Cascade]

I think that is called Butler.

 

My understanding is that the Statisticians prefer cross-IMPs as the best method.

[ciscokid]

What about having more comparisons - 30+ vs. the 15 that are done now?

 

-CK

[pclayton]

This is one of my pet peeves too; and something that I have debated a lot with a very active member of BBO that does not visit the site anymore.

 

BBO only compares 16 scores. OKB is a lot more - +/- 50-60 if I remember. You should never have a situation where you reach the optimal contract and lose IMPs, only because a few of the pairs post numbers like -2800 or +2320. Playing the board more will even out the real 'swingy' results.

 

Either have increase the number of times a board is played (shouldn't be that difficult as hundreds of tables are in play during a given hour). 16 might have been a good rule of thumb when BBO had 20-30 tables in play at once, but not now.

 

Or (an idea I like less) is to either cap the effective IMPs on a hand, or cap the maximum point score for a certain result, as it relates to IMPs.

[paulhar]

Just out of curiosity, if you're playing in the Main Bridge Club, do the other 15 results all come from the Main Bridge Club or can some of them come from the private and public clubs?

[Dwayne]

Ideally you should be removing the top and bottom scores

 

And more sensically in a tourney, only taking scores from, say, the top 10 tables after round 1.

 

Dwayne-man.

[helene_t]

My understanding is that the Statisticians prefer cross-IMPs as the best method.

Probably true. If you get +100 while a single +3200 "disaster" pertubates the mean from 0 to +200, you get -3 IMPs instead of +3. On the other hand, if you make +1100 it makes a much smaller difference if the mean is 0 or +200. Removing the extremes solves the problem to some extend but it also means that the mean IMPs made in the E-W direction is not necesarilly zero. Cross-IMPs is a more elegant solution to the problem.

[hotShot]

The IMP scale should make sure, that playing 3NT+1 or 4Major makes an imp difference of 0. An overtrick should make not much of a difference but a missed game or an undertrick should cost.

 

But if some major desaster moves the mean it can suddenly make a difference. This is why scoring to a mean requires cutting the extremes off.

 

With CrossIMPs the IMP's with every other result are calculated und you get the mean of them. This is quite fair but, if you play 10 boards with the same result that most others have, your CrossIMP score will not be 0. Usually it will be negative, because someone playing your side scored big.

 

How could that be improved?

Perhaps by shifting the calculated crossIMPs. e.g. If i have 16 results, i calculate the mean of the ordered crossIMPs 8 and 9 and shift all IMPs that way that this gets 0. That way we could have the "average result" with 0 IMPs and differences from cossIMPs.

[TimG]

With CrossIMPs  the IMP's with every other result are calculated und you get the mean of them. This is quite fair but, if you play 10 boards with the same result that most others have, your CrossIMP score will not be 0. Usually it will be negative, because someone playing your side scored big.

Usually negative? Every time it is negative for you, it is positive for your opponents.

[hotShot]

With CrossIMPs  the IMP's with every other result are calculated und you get the mean of them. This is quite fair but, if you play 10 boards with the same result that most others have, your CrossIMP score will not be 0. Usually it will be negative, because someone playing your side scored big.

Usually negative? Every time it is negative for you, it is positive for your opponents.

Hi Tim!

 

Take a look at this simple tourneyresult:

 

Example Tournament

 

It shows 39 +IMPs to 45 -IMPs sum tham up and you get -6 IMPs.

Meaning a pair having the average result at every board would have a score of -6 IMPs.

 

You can look at other tourneys if you like, but it's the same (but don't get a survivor ...)

 

Playing the average result each of e.g.10 boards will result in a negative crossIMP score.

[inquiry]

Uhhh.. hotshot....

 

what you are talking about is a tounrments online where people fail to finish a board in time. When this happens, the software assigns both sides average minus, and as a result, the net imps will be minus... (the size of minus depends upon frequency of people not finishing a round).

 

If you look at an untimed tourment, or a team match, you will find, that in fact, Tim is absoluately correct.. For every imp one side gets, the other side doesn't get... and it averages out perfectly.

 

Here is a link to an random team game http://bbo.bridgebase.com:81/tourneyresult...17242%7E744.lin

 

So, if you find an untimed tourment, or a team game, or a tourment where no procedure penalties were issued... Tim would be 100% correct...

 

Ben

[TimG]

Take a look at this simple tourneyresult:

 

Example Tournament

 

It shows 39 +IMPs to 45 -IMPs sum tham up and you get -6 IMPs.

Meaning a pair having the average result at every board would have a score of -6 IMPs.

I'm not convinced that's what it means. Can you provide a link to the travellers for this tournament?

[hotShot]

...

 

 

Here is a link to an random team game http://bbo.bridgebase.com:81/tourneyresult...17242%7E744.lin

 

So, if you find an untimed tourment, or a team game, or a tourment where no procedure penalties were issued... Tim would be 100% correct...

 

Ben

Uhhh Ben

 

how can you score a team game with crossIMPs ?

(But you are right taking a tourney like that was wrong.)

 

The problem occurs only if you have more than one result.

 

Take a look at this board:

Example traveler

 

We have:

6 times 6♠ +1 1460 2.21 IMPs N/S

12 times 6♠= 1430 1.126 IMPs N/S

once 5♠+1 680 -11.63 IMPs N/S

once 7♠X-1 -200 -16.79 IMPs N/S

 

So every of the 12 EW pais that joined the 6♠= club leave the board with -1.26 IMP's for doing everything right.

 

If you cut of the 2 extreme scores they would have been rewarded with about +0.5 IMP for not allowing the overtrick.

 

Hope i made myself clear this time.

[TimG]

The problem occurs only if you have more than one result.

 

I think you mean more than one comparison. It's hard to IMP a single score.

 

We have:

6  times 6♠ +1 1460 2.21 IMPs N/S

12 times 6♠= 1430 1.126 IMPs N/S

once 5♠+1 680 -11.63 IMPs N/S

once 7♠X-1 -200 -16.79 IMPs N/S

 

So every of the 12 EW pais that joined the 6♠= club leave the board with -1.26 IMP's for doing everything right.

 

Every one of the 12 NS pairs that joined the 6♠= club leave the board with +1.126 for doing what was routine. I think this example is a perfect counter to your claim:

Usually it will be negative, because someone playing your side scored big.

This time the NS pairs who did the routine thing got a positive result and the EW pairs who did the routine thing got a negative result. I'm still at a loss for how it can be "usually negative".

[hotShot]

Well you see my point.

 

1) It is usually negative, if someone on your side scores big.

And you notice!

 

2) It is usually positive, if the big score is at the other side.

And you don't care why it's good.

[TimG]

Well you see my point.

Actually, it seems you have seen my point. :huh:

[1eyedjack]

So every of the 12 EW pais that joined the 6♠= club leave the board with -1.26 IMP's for doing everything right.

And each of the 12 EW pairs have scored the same as each of the other EW pairs who did the same thing. So no individual EW pair has gained or lost against any other EW pair who has done the same thing. So what is the problem?

 

In real life you do not score all your results against par. You score them against what happens at the other table. If you were playing a simple teams of 4 match, and you bid and make a routine 4S when your opponents go overboard for no reason and bid a ridiculous 6S - 2 at the other table, would you suggest that at your table you should just score a flat zero because you did the routine thing? No, you would would take the 10 imps from scoring your routine result against the other table's ridiculous result.

 

That is all that is happening in a cross-imped pairs scoring. You are just playing 15 or so separate teams matches.

[hotShot]

Well 1eyedjack,

 

do we have seperate results for EW and NS in tourney results here at BBO?

 

No, we don't.

 

24 Pairs played the "par contract" at this boards, but half of them gets +1.26 and the other half -1.26.

Now look at any tournament what a difference 2.5 IMPS does in the middle reagion.

Imagine a swiss movement, each group of 12 is seated against each other.

If they score the "par contract" there,

half of them will be rewarded with the "plus score"

- the other half wih the "minus score".

Pairs of the same strength will get different IMP-Scores.

 

This is unfair!

 

So one would have to create 2 results, as in a full Mitchel-Movement

or adjust the scale, so that the par of each board is leveled to 0.

[paulhar]

24 Pairs played the "par contract" at this boards, but half of them gets +1.26 and the other half -1.26.

This is unfair!

No, not unfair at all. The side that got +1.26 IMPs reached the par contract, something that some others their way didn't do. So, in effect, they risked being one of the pairs who didn't, and if they had been one of those, they would have lost mucho imps. This pair had to do something right to reach par, something that not every pair would do. So they should be plus IMPs since other pairs did not do that something right.

 

The other side lost IMPs for playing against somebody who did something right, the way it is in any bridge game. The total avaliable IMPs available to their direction is zero. Just because their opponents bid the par contracct, they lose a couple IMPs. If they had happened to play against one of the pairs who didn't, they would have won many IMPs.

 

Would you prefer a system where the side that bids par gets nothing while if they don't reach it, they lose a bunch (heads, I break even, tails I lose bigtime), while the other side gets +0 IMPS with a shot to win the lottery if their opponents mess up? Now, THIS system seems unfair to me.

[inquiry]

hotshot...

 

I want to take continued exception to your view. Let's look at the very tournment you used in your example. This was a funny tournment consisting of two tables... As you noted the plus imps was 39 and the minus imps was 45. But if you look at the second board you will find... this result

 

17:03  ulra myri Luna 11 gosito 3NS+2 660 12.00 Movie

17:11  TonyTV1 hepto GENTELMEN RBG A-- 0 0.00 Movie

 

As you can see table two didn't finish so both players got assigned an average minus. As a surpise, Average minus is -3 imps. The software then ignored the 12 imps shown above (since 0 didn't count)... this explains the minus 6 imps in total imps.

 

But lets look at a larger event.. here is one that you played in...

Time North South East West Result Points Score Movie

15:15 Frauke herfriedm chot loa_dk 6HS+1 1010 10.14 Movie

15:12 mareksta ghjakub IVAN P KASTEL 6HN= 980 9.85 Movie

15:15 11ayaz ayserkal qirst cybergreeg 6HS= 980 9.85 Movie

15:11 luciole17 6-Jun nese_ulku Dadlum01 6HS= 980 9.85 Movie

15:09 wolfbay1 newmoon utku_oz dnmthts 6HS= 980 9.85 Movie

15:12 ongstad longisland ilevar ckk 6DS+1 940 9.21 Movie

15:13 bonnieB akade yowisz JULINEK1 6DS= 920 9 Movie

15:12 TomJ MPA pcristian tibja 6DS= 920 9 Movie

15:14 Mati pijush ephesus ege2007 6DN= 920 9 Movie

15:11 redskin JuanitaP Riekske tpv05 6DN= 920 9 Movie

15:12 jszyma tekla litlasvela odda1 6DN= 920 9 Movie

15:14 aragon_21 cipibacsi Lukasz1982 martham 6DN= 920 9 Movie

15:14 masterpaul galathea wenek wwwbbb 2SEx-4 800 7.02 Movie

15:11 oscar03 bexy1 hfb boikoo 4HNx+2 790 6.71 Movie

15:12 roman512 adka patanberna mihailau 5CWx-3 500 1.52 Movie

15:11 yazonvarda alvito hou465 MilMar 3NN+3 490 1.06 Movie

15:09 Mirek7 kosiorek savagel ibinwid 4HS+2 480 0.89 Movie

15:11 zbig1959 kaktus panni andi13 4HN+2 480 0.89 Movie

15:09 jw_nl Florian mitkog makiigoca 4HS+2 480 0.89 Movie

15:10 missis krol Simo RZ GoroDim 4HN+2 480 0.89 Movie

15:09 Gavnick AdiPus nabla belzebub 4HS+2 480 0.89 Movie

15:08 hanske omrgen Majka 9 klx123 4HN+2 480 0.89 Movie

15:09 meto jeromeD Miriglio trescan 4HN+2 480 0.89 Movie

15:12 alinac adimaxi cetsa mstfdal 4HN+2 480 0.89 Movie

15:11 edigi S111 gidut0 peppoo_815 4HN+2 480 0.89 Movie

15:10 zika-ri mpb azmat moldinn 4HN+2 480 0.89 Movie

15:11 SuzanneG rita410 Sandra_ asure 4HN+2 480 0.89 Movie

15:11 2kiepy Trykacz adi_agm tal99_2000 4HS+2 480 0.89 Movie

15:11 likier okinu amog jerzyo48 3NS+2 460 0.38 Movie

15:10 senwl marsal24 pest 43 opela 3NN+2 460 0.38 Movie

15:09 mandraketr keithed Christiana Milen39 3NN+2 460 0.38 Movie

15:12 maxele dknobb markosz leszek1 3NS+2 460 0.38 Movie

15:12 02klon szu iandy65 fulvio2002 5HN= 450 0.36 Movie

15:11 saskay Tolja Lucynka Parys 4HN+1 450 0.36 Movie

15:10 mauricf ediz juupar 586 4HN+1 450 0.36 Movie

15:12 kaz5 wiechu_51 damya skamandar 4HN+1 450 0.36 Movie

15:09 misanek radka1 Bolur Ewil 4HN+1 450 0.36 Movie

15:11 carlotta_ RIOLO937 takao92 teodg 4HN+1 450 0.36 Movie

15:10 gok_man bridgenaut jb_ivanov M_A_T 5HS= 450 0.36 Movie

15:10 iittt saphire_10 vanilla theking_eg 4HS+1 450 0.36 Movie

15:11 pepe65 tabacc elichris tbdalak 4HS+1 450 0.36 Movie

15:09 b2329 roman01 tem2022 nuket450 4HS+1 450 0.36 Movie

15:10 kimiec3 witold50 jaheim Aurland 4HS+1 450 0.36 Movie

15:12 gonfarone kalluin rob145 marco1961 5DN+1 420 -0.55 Movie

15:09 1nico iu10ba mstokn hahin 4HS= 420 -0.55 Movie

15:13 DENAR jacky23 broccolo redbaron 5DS+1 420 -0.55 Movie

15:10 butterfly6 sjp garozzo_bg tuppachi 5DN+1 420 -0.55 Movie

15:10 baarbland satto_dk Ninie krasy 5DS+1 420 -0.55 Movie

15:09 sers asib marisa480 star 39 5DN= 400 -0.94 Movie

15:13 marian6 lokis2 alisa 1 Scorpio13 5DS= 400 -0.94 Movie

15:11 1sq ducich ellie26 cfop 5DN= 400 -0.94 Movie

15:11 heval bersan dwei59 tafkah 4DN+2 170 -5.24 Movie

15:11 001ibo bilge_25 HOTSHOT annmarye 2DN+4 170 -5.24 Movie

15:10 Gigolo_HD snowfox evasu oscarino 6HN-1 -50 -9.09 Movie

15:13 yaho ado47 andrzej8 Arkadisz 4HN-1 -50 -9.09 Movie

15:11 emre__ p_r_e_n_ss biasov1 jogiii 6HS-1 -50 -9.09 Movie

15:15 ja 1 c 69 ljl69 alpayge deniz74 6DN-1 -50 -9.09 Movie

15:12 meral44 bacilluss hrothgar Free 6HN-1 -50 -9.09 Movie

15:14 tessa32 linoline olegario Jan nl 6HS-1 -50 -9.09 Movie

15:10 swiftursul basca bridgeboy malucy 4HS-1 -50 -9.09 Movie

15:11 burhancem aykuti big60 aloha1 3NN-1 -50 -9.09 Movie

15:09 Stefan_wj Marcopol senol1 Akcaoglu 3NN-1 -50 -9.09 Movie

15:14 safra MASTIFF fkont janni 6DN-1 -50 -9.09 Movie

15:12 RF saltdevil malte Preempt777 3NN-1 -50 -9.09 Movie

15:12 kolhen milkica tis1 RAR60 6DN-1 -50 -9.09 Movie

15:14 leader805 chiquitina dalem123 rop 6HS-2 -100 -9.7 Movie

15:09 BN64985 highdel macu71 napp0 6HS-3 -150 -10.47 Movie

      -0.08

 

and another board

 

Time North South East West Result Points Score

15:46 garozzo_bg tuppachi chot loa_dk 3HEx-2 300 8.56

15:43 senol1 Akcaoglu safra MASTIFF 2CN+2 130 5.32

15:46 evasu oscarino TomJ MPA 2SN= 110 4.47

15:46 mstokn hahin andrzej8 Arkadisz 2SN= 110 4.47

15:45 Miriglio trescan luciole17 6-Jun 2SN= 110 4.47

15:46 iandy65 fulvio2002 Simo RZ GoroDim 2CN+1 110 4.47

15:45 hanske omrgen 11ayaz ayserkal 3CN= 110 4.47

15:45 pcristian tibja jw_nl Florian 2CN+1 110 4.47

15:43 ongstad longisland wolfbay1 newmoon 3CS= 110 4.47

15:44 tis1 RAR60 HOTSHOT annmarye 3CN= 110 4.47

15:44 mandraketr keithed big60 aloha1 2CN+1 110 4.47

15:44 swiftursul basca edigi S111 2CN+1 110 4.47

15:44 macu71 napp0 wenek wwwbbb 2CN+1 110 4.47

15:44 maxele dknobb gidut0 peppoo_815 2SN= 110 4.47

15:46 biasov1 jogiii cetsa smoz 3DE-2 100 4.45

15:47 zbig1959 kaktus meto jeromeD 3DEx-1 100 4.45

15:44 senwl marsal24 marian6 lokis2 1SN= 80 4.06

15:43 pepe65 tabacc baarbland satto_dk 1SN= 80 4.06

15:44 mareksta ghjakub likier okinu 2NW-1 50 3.15

15:44 2kiepy Trykacz kimiec3 witold50 3NW-1 50 3.15

15:42 azmat moldinn yazonvarda alvito 4DE-1 50 3.15

15:42 zika-ri mpb jszyma tekla 3DE-1 50 3.15

15:45 Mati pijush ephesus ege2007 1SN-1 -100 -0.33

15:43 savagel ibinwid Majka 9 klx123 2SN-1 -100 -0.33

15:46 mauricf ediz marisa480 star 39 3SN-1 -100 -0.33

15:45 carlotta_ RIOLO937 Frauke herfriedm 3CN-1 -100 -0.33

15:44 panni andi13 Gavnick AdiPus 2SN-1 -100 -0.33

15:47 butterfly6 sjp juupar 586 2SN-1 -100 -0.33

15:44 alisa 1 Scorpio13 alinac adimaxi 2SN-1 -100 -0.33

15:45 1nico iu10ba DENAR jacky23 2SN-1 -100 -0.33

15:44 Bolur Ewil IVAN P KASTEL 2SN-1 -100 -0.33

15:48 02klon szu takao92 teodg 2SN-1 -100 -0.33

15:48 missis krol yaho ado47 2SN-1 -100 -0.33

15:45 hfb boikoo qirst cybergreeg 2CN-1 -100 -0.33

15:46 broccolo redbaron Lucynka Parys 3CN-1 -100 -0.33

15:45 pest 43 rbl71 sers asib 2SN-1 -100 -0.33

15:45 gonfarone kalluin amog jerzyo48 2SN-1 -100 -0.33

15:45 yowisz JULINEK1 emre__ p_r_e_n_ss 1SN-1 -100 -0.33

15:42 Christiana Milen39 jb_ivanov M_A_T 2SN-1 -100 -0.33

15:42 malte Preempt777 Sandra_ asure 2SN-1 -100 -0.33

15:42 Riekske tpv05 redskin JuanitaP 2SN-1 -100 -0.33

15:41 patanberna mihailau bridgeboy malucy 2SN-1 -100 -0.33

15:41 Ninie krasy gok_man bridgenaut 2SN-1 -100 -0.33

15:43 ellie26 cfop Stefan_wj Marcopol 2SN-1 -100 -0.33

15:42 jaheim Aurland alpayge deniz74 2SN-1 -100 -0.33

15:41 tessa32 linoline adi_agm tal99_2000 2SN-1 -100 -0.33

15:42 leader805 chiquitina utku_oz dnmthts 2SN-1 -100 -0.33

15:41 roman512 adka masterpaul galathea 3DE= -110 -0.53

15:43 aragon_21 cipibacsi dalem123 rop 1NW+2 -150 -1.73

15:47 oscar03 bexy1 damya skamandar 3SN-2 -200 -2.94

15:45 rob145 marco1961 saskay Tolja 3SN-2 -200 -2.94

15:46 kaz5 wiechu_51 mitkog makiigoca 2SN-2 -200 -2.94

15:45 bonnieB akade misanek radka1 3SN-2 -200 -2.94

15:44 fkont janni vanilla theking_eg 2SN-2 -200 -2.94

15:41 elichris tbdalak b2329 roman01 3SN-2 -200 -2.94

15:43 SuzanneG rita410 001ibo bilge_25 3SN-2 -200 -2.94

15:43 iittt saphire_10 tem2022 nuket450 3SN-2 -200 -2.94

15:41 BN64985 highdel burhancem aykuti 2SN-2 -200 -2.94

15:41 ilevar ckk 1sq ducich 2SN-2 -200 -2.94

15:43 cygato saltdevil litlasvela odda1 2SN-2 -200 -2.94

15:42 Lukasz1982 martham heval bersan 2SN-2 -200 -2.94

15:41 hrothgar Free dwei59 tafkah 2HN-3 -300 -5.14

15:44 nabla belzebub Mirek7 kosiorek 3NW= -400 -7.12

15:46 nese_ulku Dadlum01 Gigolo_HD snowfox 4SN-4 -400 -7.12

15:45 olegario Jan nl ja 1 c 69 ljl69 2SNx-2 -500 -8.85

15:42 asthana leszek1 kolhen milkica 3SNx-2 -500 -8.85

15:44 hou465 MilMar meral44 bacilluss 4CNx-4 -1100 -14.21

      0.06

 

The first one had an average imp score of -0.08 over 68 hands, the second a plus 0.06 over the same number. This small difference is due to rounding error. For all practical purposes this is zero. As it should be.

 

Ben

[uday]

Just out of curiosity, if you're playing in the Main Bridge Club, do the other 15 results all come from the Main Bridge Club or can some of them come from the private and public clubs?

 

All these deals come from the same pool of deals. So could be from priv/public clubs

[jtfanclub]

Well 1eyedjack,

 

do we have seperate results for EW and NS in tourney results here at BBO?

 

No, we don't.

Isn't that the real problem?

 

Let's say you have a big tourney IRL with Mitchell movement. All of the North-Souths stay as N/S thoughout the tourney, and same for West. All of pairs are experts except one...who joined as a joke and never stops below the 6 level. If that pair sits E/W, then any N/S pair who doesn't play them is absolutely screwed.

 

I can think of a couple ways to solve this in larger tourneys. One, which already exists, is having the 1st, 3rd, 5th, etc. teams sit N/S and 2nd, 4th, 6th etc. sit E/W. I don't know if there is a good way in the main bridge club, though. Maybe using only the 'middle' 32 results instead of the first ones. You know, now that I think about it, that shouldn't be tough to program, right? B)

[helene_t]

The IMP scale should make sure, that playing 3NT+1 or 4Major makes an imp difference of 0. An overtrick should make not much of a difference but a missed game or an undertrick should cost.

But if some major desaster moves the mean it can suddenly make a difference. This is why scoring to a mean requires cutting the extremes off.

No. In a teams match, 3NT+1 may or may not be better than 4M= depending on the result at the other table. For example, if the other table make 1CX+3 = 440 then 3NT+1 is 0 IMPs and 4M= is -1 IMPs. Actually, if a "disaster" pertubades the average, the probability that 3NT+1 will score more than 4M= decreases.

 

The rationale for removing the extremes is this: suppose that there is a probability of 2% of making a -4000 disaster. This will happen on 32% of all boards in a 16 table tourney, and it will pertubade the mean with 4000/16 = 250. When converted to IMPs, a 32% chance of a 250-pertubation is worse than a 2% chance of a 4000-pertubation. Therefore, without removing the extremes, butler would be more sensitive to disasters than a team match. But, as allready said, chross-IMPs is a better solution to the same problem.

[mink]

Hi Robert (hotshot),

 

I agree with Helene that cross-IMPs already compensates most of the problem that Butler tries to avoid by ommitting the extremes when calculating the average. But your example shows that still the pairs who bid and made 6S earn 1.26 IMPs for just doin the normal thing. And their opps lose that IMPs without doing anything wrong. So you still like that those who reach the par score not compared against the extremes.

 

Unfortunately you do not provide an algorithm that determines what is an extreme and how many are to be avoided. And should the extremes be compared against other extremes or not?

 

Even if you leave the extremes out, those pairs that make no overtrick would get -0.33 IMPs and the ones with overtrick would get +0.72 IMPs. But the NS pairs cannot do anything about the overtrick - it just depends on wether the opps lead their ♣A or not. Of course this kind of problem can never be avoided unless you assign scores for each result and side manually. But it has about the same magnitude like the one that you like to avoid.

 

And there is another problem with leaving out the extremes: Imagine in some other board all pairs play 6♠ and go down because of opps leading a singleton to partners A and get a ruff, but one pair bids 6nt that makes. This time, the 6♠ declarers deserve to lose some IMPs. According to your intention one could argue that 6nt= is the par score here and this pair should get 0 IMPs and all others -14 IMPs each.

 

Conclusion: You run in too many problems if you try to enhance the scoring. Better just leave the cross-IMPs as they are.

 

Karl