Computer Scoring IMP pairs
#1
Posted 2014-April-29, 10:02
IMP Pairs 15 tables Skip Mitchell 15 EW phantom pair 12 rounds 24 boards
In the scoring program i use the computer gives following options among other things.
1) cross imp / comparisons
2) cross imp pairs / SQR(rc/2)
3) Butler Pairs
4) Aggregate scoring
Rightly or wrongly I chose method 2 although I do not know how it works.
On a particular board 3 pairs bid Vul game 8 pairs bid vulnerable slam and 1 pair bid grandslam.
The pair that bid grandslam was awarded 19.08 IMPS.
How is that possible. The datum is just about 1400.
Does method 2 have some different way of calculating datum? Should I use some other option?
Can someone please explain
Do unto others as you would have others do unto you.
"Mediocrity knows nothing higher than itself, but talent instantly recognizes genius".
#2
Posted 2014-April-29, 10:27
#3
Posted 2014-April-29, 10:58
#4
Posted 2014-April-29, 11:36
Bbradley62, on 2014-April-29, 10:58, said:
yes all made their contracts. The 12 scores were 1370/1390/720/1470/1390/1470/2220/1470/1440/620/640/1390.
The contracts were 3NT/5C/6C/6NT/7NT making 12 or 13 tricks (depending on whether Club Queen was guessed or not.
Do unto others as you would have others do unto you.
"Mediocrity knows nothing higher than itself, but talent instantly recognizes genius".
#5
Posted 2014-April-29, 11:41
#6
Posted 2014-April-29, 12:13
vulnerable, 7NT= will make 13 imps against all small slams; 17 against the games. Add 'em up, we get 8 13s and
[Edit: can't count to 12 after all these years of counting to 13. Argh.]
* GordonTD has it below. "rc" is 11*12. I have no idea why yet, but I'm sure all will be explained in time.
#7
Posted 2014-April-29, 12:30
#8
Posted 2014-April-29, 13:31
mycroft, on 2014-April-29, 12:13, said:
vulnerable, 7NT= will make 13 imps against all small slams; 17 against the games. Add 'em up, we get 8 13s and 4 17s, for 172. To get 19.08 IMPs, we'll be dividing by 9ish. I have no idea where that number comes from, but it's sqrt(rc/2), and that is supposed to "reflect teams scoring". It looks like dividing by 9ish rather than 11 (EBU) or 12 (ACBL) is going to inflate the IMP score, but the key number isn't the 19.08, it's the 172.
The method should be as Mycroft said. The actual x-IMP for the board should be roughly 14.1 (8x13+3x17)/11. It's not clear how the software showed 19.08.
Guess the correct option in the software for IMP scoring should be #1 - cross-imp comparisons.
#9
Posted 2014-April-29, 16:05
zasanya, on 2014-April-29, 10:02, said:
Really? How does that work?
London UK
#10
Posted 2014-April-29, 16:27
shyams, on 2014-April-29, 13:31, said:
(8x13+3x17)/sqrt((11x12)/2)=19.08
shyams, on 2014-April-29, 13:31, said:
Yes

London UK
#11
Posted 2014-April-29, 17:07
I found the manuals for this scorer, and it was - unhelpful on this point. Almost as if if we wanted to use this scoring method, we'd already know all about it. Sort of like a "multiple teams movement".
Again, though, it doesn't matter what the "divided by" is, at least for the scoring (okay, factoring, yeah); it's the raw IMP score from all the comparisons that matters. Bringing it down to a "reasonable" number that we're all used to from single-comparison teams scoring, by dividing by some reasonable, constant factor is just for our feeble brains.
#12
Posted 2014-April-30, 01:52
mycroft, on 2014-April-29, 17:07, said:
r=results
c=comparisons
So I should really have written 12*11, not 11*12.
There has long been friendly disagreement between scoring experts about whether one should divide by the number of results or the number of comparisons, but the truth, as you say below, is that it doesn't matter much unless the numbers are small and you try to compare results scored by the two different methods.
mycroft, on 2014-April-29, 17:07, said:
Well since the scorer comes from England where "multiple teams movement" is standard terminology, it's hardly surprising that there's no need to explain it. However I think you are correct that no-one who didn't already know about this obscure scoring method would want to use it. The only document that I could find that mentions this formula does so in the context of a more complex discussion about constructing VP tables and doesn't really answer your question.
mycroft, on 2014-April-29, 17:07, said:
London UK
#13
Posted 2014-April-30, 02:11
-- Bertrand Russell
#14
Posted 2014-April-30, 02:18
mgoetze, on 2014-April-30, 02:11, said:
Except that they are dividing the geometric mean by sqrt(2), so the final results are all much larger than when dividing by either results or comparisons.
I'll try to find out more about this.
London UK
#15
Posted 2014-April-30, 03:00
gordontd, on 2014-April-29, 16:05, said:
Sorry standard mithchell amd there was no phantom pair but that doesnt essentially change the IMP problem?
Do unto others as you would have others do unto you.
"Mediocrity knows nothing higher than itself, but talent instantly recognizes genius".
#16
Posted 2014-April-30, 03:03
gordontd, on 2014-April-30, 02:18, said:
I'll try to find out more about this.
Thank you Sir.
Do unto others as you would have others do unto you.
"Mediocrity knows nothing higher than itself, but talent instantly recognizes genius".
#17
Posted 2014-April-30, 03:10
zasanya, on 2014-April-30, 03:00, said:
No, it doesn't change it - I was just intrigued to find out more about this unknown movement!
London UK
#18
Posted 2014-April-30, 05:06
gordontd, on 2014-April-29, 16:05, said:
I suspect 30 boards in play, but pairs play only 24.
"Robin Barker is a mathematician. ... All highly skilled in their respective fields and clearly accomplished bridge players."
#19
Posted 2014-April-30, 06:58
RMB1, on 2014-April-30, 05:06, said:
For IMP pairs this is even worse than arrow-switching.
#20
Posted 2014-April-30, 07:09
Vampyr, on 2014-April-30, 06:58, said:
Yes. And, what fun at cross-IMPs. There could be hundreds of IMPs available to some pairs and not to others.