[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

Quote

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...

Quote

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]

Quote

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]

hotShot, on Aug 12 2004, 04:43 PM, said:

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?

[helene_t]

hotShot, on Aug 12 2004, 04:03 PM, said:

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

[hotShot]

This is the score with crossIMPs

6 times 6♠ +1 1460 2.21 IMPs N/S
12 times 6♠= 1430 1.26 IMPs N/S
once 5♠+1 680 -11.63 IMPs N/S
once 7♠X-1 -200 -16.79 IMPs N/S

This is how it should be:
6 times 6♠ +1 1460 1 IMPs N/S
12 times 6♠= 1430 0 IMPs N/S
once 5♠+1 680 -13 IMPs N/S
once 7♠X-1 -200 -17 IMPs N/S

(As you can see Ben, the sum of the N/S scores is not 0 and i don't care.)


As we see the board is not very selective and the score does not split the field.

How can that be reached:

a) In a Butler way:
Eliminate 2 Scores at top and buttom, and calcucate the mean:
(12 * 1430 + 4*1460 ) /16 = 1438
score all pairs against this result.

b ) using the "median"
Meaning sorting the scores for NS by value and taking the one in the middle
(with an even number you middle the two closesed to that)
we have 20 scores here sorted scores 7-18 are 1430 so the median is 1430.

c) minimize the "absolute sum of IMPs"
At crossIMPs there were:
(6*2.21 + 12* 1.26 + 11.63 + 16.79) * 2 = 113,6
As it should be:
(6*1 + 12*0 + 13 + 17) * 2 = 72

Using crossIMPs in a tourney means that players making/defending the "par contract" will randomly get +/-IMP depending on which side the big scores/mistakes were made at another table.
Selection is done by seating not by bridge abilities.

The way i think it should be, seating is not (at least much less) selective.

This is my final post to this topic.

[inquiry]

hotShot, on Aug 13 2004, 02:56 PM, said:

This is my final post to this topic.

Well Good, Tim and I always like getting last word...

Ok, I will try one last time, for what it is worth. You first made a characterization above, looking at a tournment result where the net imps was minus SIX that this difference was because of some problem with cross imps. Even telling the world they could check any tournment and it would always be negative imps (as long as not survivor).

I pointed out why your example was flawed (average minuses for both NS pair added in, which accounted for the minus six imps).. Then I followed that up with two boards from a tournment you played in to illustrate the point that it really does add up to zero.

Even the TRAVELLER you present the NS scores do in fact sum up to ZERO despite your claim to otherwise (cut and past travelle rinto EXCEL and sum the column) (actualy it sums to minus 0.04 due to rounding errors). If you carried out the math to 9 decimal places, this becomes zero. It was this arguement you made, that the SCORE DOESN"T COME to ZERO that I was, and always have addressed.

Since you are going to stop posting, I will go ahead and address your other point. Which is on the hand given, the RESULT should be +1430 or maybe +1460... so haow come a +1430 is anything other than zero? Well this is a very hard standard to enforce. Lets say that 101 tables play a hand, and one pair bids 6S makes and all other bid 4S and make 6. What do you score in your example.. Should all the 4S bidders get minus 13 imps, since slam always make? I think with your example perhpas that is what should happen. But who judges 6sp is right.

The second arguement is cross imps cut the wrong way, so for the normal result you typically get a minus reesult. Well, that is out and out wrong. Let's take a simple example, you 6S example earlier.

6S is normal, so each NS pair here for the normal result got a small plus, but each EW on the same hand for the normal result got a small minus (after all, they did nothing wrong either). In fact, the normal result result in a net average (small plus for one side, small minus for the other). Sometimes you will bid a perfectly normal game, and make and get a small minus because a few agreesive people bid a horrible slam that should have no chance, but somehow made. Or you might get a small plus because some bid slam and went down and others couldn't find their way to game. I suggest you ignore these small differences, the extra work you propose and the extra calcuations hardly seem that would be in anyway better, and would take up valuable programmer time as well as server time. If you are this worried about the small differences, I recommend you play only matchpoints and team games... when I play "serious", I try to play teams becuase of issues that you are concerned about.

The views above are mine and mine alone as a user.. i have no idea how uday or fred feel about his issue.

Ben

[1eyedjack]

hotShot, on Aug 13 2004, 01:56 PM, said:

This is the score with crossIMPs

And next hand (all vul) the traveller shows:

19 tables 4S making exactly by N +620 to NS
1 table 5HX -2 by W for +500 to NS

Using your scoring the 19 tables score 0 Imps despite that at their tables the E/W pairs failed to find a profitable sacrifice.

Using cross imps the majority of the NS pairs get a small positive, as they deserve, having beaten par, and the EW get a corresponding negative, as they deserve.

You pays your money ...

I go with cross imps

[TimG]

Quote

This is the score with crossIMPs

6 times 6♠ +1 1460    2.21 IMPs N/S
12 times 6♠= 1430      1.26 IMPs N/S
once 5♠+1 680        -11.63 IMPs N/S
once 7♠X-1 -200      -16.79 IMPs N/S

This is how it should be:
6 times 6♠ +1 1460  1 IMPs N/S
12 times 6♠= 1430  0 IMPs N/S
once 5♠+1 680      -13 IMPs N/S
once 7♠X-1 -200    -17 IMPs N/S

(As you can see Ben, the sum of the N/S scores is not 0 and i don't care.)

Why should the EW pairs who defended 5♠ or 7♠ be rewarded? They did nothing but sit there and watch the opponents commit a blunder, yetthey get 13 or 17 IMPs.

Quote

a) In a Butler way:
    Eliminate 2 Scores at top and buttom, and calcucate the mean:
    (12 * 1430 + 4*1460 ) /16 = 1438
    score all pairs against this result.

IMPing against the mean is distorting due to the logarithmic nature of the IMP scale. Take a board where half the field scores +620 and the other half -100. All pairs will score +/- 6 IMPs = the average of the pushes and 720s (=12 IMPs). If you first take the mean = +260 and then IMP against that, all pairs will score +/- 8 IMPs (for their +/- 360 against the mean).

Quote

b ) using the "median"
    Meaning sorting the scores for NS by value and taking the one in the middle
    (with an even number you middle the two closesed to that)
    we have 20 scores here sorted scores 7-18 are 1430 so the median is 1430.

So, when there are 10 +620s and 9 -100s, everything is IMPed against +620 and when there are 9 +620s and 10 -100s, everything is IMPed against -100? I'd much rather average out this effect by IMPing against every pair and taking an average of that.

Quote

Using crossIMPs in a tourney means that players making/defending the "par contract" will randomly get +/-IMP depending on which side the big scores/mistakes were made at another table.

You can think of it as your expected score for that result given a large number of different teammates. Perhaps the reason there were more big scores/mistakes on one side of the score sheet is because the problems facing that pair were more difficult. As the number of replays increases, this ought to be closer and closer to the actuality.

Quote

This is my final post to this topic.

A sure sign that someone knows they have been beaten.

[hotShot]

Well i did not want to but...

I did not say that crossIMPs should be replaced.

I did say crossIMPs have a effect on the result, when NS and EW are mixed up in one result and extreme scores happen.

Matchpoints scoring has an effect on the result, as even a 10 point difference can give you a top.

In Totalpoint scoring there are effects an the result.


In a team match both tables either have the same result (0 IMP) or a different result leading to some IMPs.
So what i expect from an pair tourney with IMP scoring, is that a contract leads to 0 IMPs if played from most of the other players too.
At a team match the IMPs are not given compared to the best possible result, but to the (best) existing result.

I admit there are problems if you don't have a contract played by most of the others, as TimG points out.

Quote

a) In a Butler way:
    Eliminate 2 Scores at top and buttom, and calcucate the mean:
    (12 * 1430 + 4*1460 ) /16 = 1438
    score all pairs against this result.


IMPing against the mean is distorting due to the logarithmic nature of the IMP scale. Take a board where half the field scores +620 and the other half -100. All pairs will score +/- 6 IMPs = the average of the pushes and 720s (=12 IMPs). If you first take the mean = +260 and then IMP against that, all pairs will score +/- 8 IMPs (for their +/- 360 against the mean).

Well in a team match you would either have 12 or 0. I have no problem with 8 here, at least it is consitent.

Quote

b ) using the "median"
    Meaning sorting the scores for NS by value and taking the one in the middle
    (with an even number you middle the two closesed to that)
    we have 20 scores here sorted scores 7-18 are 1430 so the median is 1430.


So, when there are 10 +620s and 9 -100s, everything is IMPed against +620 and when there are 9 +620s and 10 -100s, everything is IMPed against -100? I'd much rather average out this effect by IMPing against every pair and taking an average of that.

Well i said the contract played by most of the others. I your example the majoraty is only a pair bigger than the minority.

Using crossIMPs at two boards, where all but one play a (small) slam, it will happen that my slam is only worth 1.2 IMPs (because someone did not bid it) while someone else's is worth 1.7 (because someone bid grandslam and fails with redouble). If most players make the slam, both should be avarded with 0 IMP.


I don't know how much CPU-Power your server has left, but Median and Butler scoring would require less than calculating crossIMPs. Sure the minimizing approach will cost (a little) more.

And if it would be implemented, if somebody wrote the perl script, i guess i can do it.

[1eyedjack]

hotShot, on Aug 13 2004, 01:56 PM, said:

a) In a Butler way:
    Eliminate 2 Scores at top and buttom, and calcucate the mean:
    (12 * 1430 + 4*1460 ) /16 = 1438
    score all pairs against this result.

b ) using the "median"
    Meaning sorting the scores for NS by value and taking the one in the middle
    (with an even number you middle the two closesed to that)
    we have 20 scores here sorted scores 7-18 are 1430 so the median is 1430.

c) minimize the "absolute sum of IMPs"
    At crossIMPs there were:
    (6*2.21 + 12* 1.26 +  11.63 + 16.79) * 2 = 113,6
    As it should be:
    (6*1 + 12*0 + 13 + 17) * 2 = 72

Using crossIMPs in a tourney means that players making/defending the "par contract" will randomly get +/-IMP depending on which side the big scores/mistakes were made at another table.
Selection is done by seating not by bridge abilities.

The way i think it should be, seating is not (at least much less) selective.

You appear to be suggesting three alternatives to cross imps, but despite that you have labelled them "a)", "b )", and "c)" it looks to me as though there are only two alternatives, with "c)" just being an extension of the consequences of "b )". Of the two alternatives (Butler and median) I am not sure which you are advocating as preferable, but I get the impression that it is the median method.

So, next hand you get:

10 tables in 4S making tick by N/S, +420
10 tables in 4S one off by N/S, -50.

Which would you treat as the median, against which to score all the results? +420 or -50? It makes a bit of a difference, I am sure you agree. I think from your post you are suggesting IMPing it against +235, but this seems just as random.

What if there were only 19 tables in total. You are the last table to finish and so far there are 9 tables making and 9 tables one off. You are a defender required to make a critical decision at trick 8. There are two possible layouts that might beat 4S, and you have nothing to go on. Which route you choose makes a massive difference to the scores at all 19 other tables as well as your own. Can this be an improvement on cross imps?

The flaws in Butler scoring have already been pointed out in

http://bridgebase.lunarpages.com/~bridge2/...indpost&p=20893

[EricK]

I suspect there is no perfect scoring system. But there may be one which is a bit better than the others.

On the other hand, I have never played any reasonably long session of bridge where I could honestly say that I lost or did badly because of the scoring. There are always plenty of hands where I could have played a bit better, and a few where I could have played much better. Once I have eliminated all those mistakes from my game, I shall return to the problem of determining the best scoring system.

Eric

[JRG]

TimG, on Aug 13 2004, 02:51 PM, said:

Why should the EW pairs who defended 5♠ or 7♠ be rewarded? They did nothing but sit there and watch the opponents commit a blunder, yetthey get 13 or 17 IMPs.

Uh, I disagree.

They may have been very active in the auction. They may have pushed the opponents around; they may have accelerated the bidding and given the opponents a chance to go wrong. It is quite possible they were far from passive bystanders. They may have "earned" their good result.