A scoring question Rationale behind sections
#1
Posted 2012-December-01, 21:54
So, last night at the club we were arbitrarily divided into two "sections" - each with its own set of table numbers, 9-10 tables each, eight rounds of 3 boards each. No arrow switching at any point. At the end of the evening, scoring was done for each section, then combined to create two winners, one for each axis.
Two questions:
a) What is the point of dividing into sections? I couldn't figure out how it's different from just having one section of 18 tables or however many would've been needed.
b) Does it make any sense to score matchpoints within each section and then mix the results together? It seems odd to me that on a given board, a score of 50 might be worth 80% to some pairs and 40% to other pairs seating along the same axis.
#2
Posted 2012-December-02, 02:11
Antrax, on 2012-December-01, 21:54, said:
So, last night at the club we were arbitrarily divided into two "sections" - each with its own set of table numbers, 9-10 tables each, eight rounds of 3 boards each. No arrow switching at any point. At the end of the evening, scoring was done for each section, then combined to create two winners, one for each axis.
Two questions:
a) What is the point of dividing into sections? I couldn't figure out how it's different from just having one section of 18 tables or however many would've been needed.
b) Does it make any sense to score matchpoints within each section and then mix the results together? It seems odd to me that on a given board, a score of 50 might be worth 80% to some pairs and 40% to other pairs seating along the same axis.
How can you play 27 boards with 18 tables ? If you play one-board-per-round you have to then do another half a round, not very fair. If you play two-boards-per-round then you won't complete the 36-board movement.
Yes, you can just matchpoint within each section, but you might as well have the same boards in both sections and get more comparisons.
#3
Posted 2012-December-02, 02:49
b) No, it's wrong to matchpoint the sections independently. Doing this takes away the benefit of having two sections.
#4
Posted 2012-December-02, 03:44
Thanks gnasher, those were my guesses too. Though I do wonder, if you have two sets of identical boards, can't you just number boards 10-18 as 1-9 again and compare? Nobody is going to play a board twice anyway.
#5
Posted 2012-December-02, 08:38
Antrax, on 2012-December-01, 21:54, said:
So, last night at the club we were arbitrarily divided into two "sections" - each with its own set of table numbers, 9-10 tables each, eight rounds of 3 boards each. No arrow switching at any point. At the end of the evening, scoring was done for each section, then combined to create two winners, one for each axis.
Two questions:
a) What is the point of dividing into sections? I couldn't figure out how it's different from just having one section of 18 tables or however many would've been needed.
b) Does it make any sense to score matchpoints within each section and then mix the results together? It seems odd to me that on a given board, a score of 50 might be worth 80% to some pairs and 40% to other pairs seating along the same axis.
a) The point is to get a reasonable number of boards in the time available. An N-table Mitchell movement requires N rounds to be complete. If you have 18 tables, you need 18 rounds. At two boards (and roughly 15 minutes) per round, that's 4.5 hours for the game, plus any "admin" time. If you split into two sections, you can play nine three board rounds (27 boards) at 22.5 minutes per round, and be done in about 3.5 hours.
b} "Overall" scores combine both sections into one field, so the number of matchpoints anyone gets for any particular score on a given board will be the same. The downside (I think, I haven't looked at it in some time) is that the scoring program (I'm referring here to ACBLScore, other programs may not do this) treats NS and EW in a Mitchell as part of the same field when computing overall scores, which makes no sense unless you arrow switch, thus getting a "one winner" movement.
As for tv, screw it. You aren't missing anything. -- Ken Berg
I have come to realise it is futile to expect or hope a regular club game will be run in accordance with the laws. -- Jillybean
#6
Posted 2012-December-02, 09:30
blackshoe, on 2012-December-02, 08:38, said:
You don't have to play a complete Mitchell.
An 18-table Mitchell ending after 9 rounds is better than two 9-table Mitchells scored independently. In either movement you play nine rounds against nine different opponents, with eight comparisons per board. The incomplete 18-table movement is better because each pair's score for the session is affected by the actions of the entire field, rather than just half of it.
The benefit of splitting into two sections exists only if you score across the sections. You still play nine rounds against nine different opponents, but you have 24 comparisons per board, and your score on each board is affected by the actions of every other player.
This post has been edited by gnasher: 2012-December-02, 09:33
#7
Posted 2012-December-02, 09:58
Antrax, on 2012-December-02, 03:44, said:
Thanks gnasher, those were my guesses too. Though I do wonder, if you have two sets of identical boards, can't you just number boards 10-18 as 1-9 again and compare? Nobody is going to play a board twice anyway.
To get dealer and vulnerablity right, you will have to use boards 1-9, and 17-25, not 10-18.
#8
Posted 2012-December-02, 12:40
paua, on 2012-December-02, 02:11, said:
Yes, you can just matchpoint within each section, but you might as well have the same boards in both sections and get more comparisons.
Another option for 18 boards is to do a Web. I think you can do 24 or 26 or 28 boards.
#9
Posted 2012-December-03, 01:35
gnasher, on 2012-December-02, 02:49, said:
I don't disagree with you about theory, but many clubs around here do that so that if a board is misduplicated or fouled in some other way, only one section is affected.
#10
Posted 2012-December-03, 01:40
Antrax, on 2012-December-01, 21:54, said:
a) What is the point of dividing into sections? I couldn't figure out how it's different from just having one section of 18 tables or however many would've been needed.
Some clubs may not have boards numbered high enough for having all people in one section. We have sets of 36 boards so when we have 18.5+ tables, we HAVE to go to two sections. And then sometimes someone doesn't show up, so we have two nine table sections.
And yes, there are movements that use two sets of boards in one big movement. If you can trust players to move boards correctly, this is feasible but if you don't, then you can't do this.
#11
Posted 2012-December-03, 17:33
gnasher, on 2012-December-02, 09:30, said:
An 18-table Mitchell ending after 9 rounds is better than two 9-table Mitchells scored independently. In either movement you play nine rounds against nine different opponents, with eight comparisons per board. The incomplete 18-table movement is better because each pair's score for the session is affected by the actions of the entire field, rather than just half of it.
The benefit of splitting into two sections exists only if you score across the sections. You still play nine rounds against nine different opponents, but you have 24 comparisons per board, and your score on each board is affected by the actions of every other player.
You don't have to complete any movement. The problem with your curtailed 18 table Mitchell is that not everyone plays the same boards.
I have no problem with two sections playing the same boards and scoring "across the field", so long as if there are no error switches there are still two fields - NS and EW. I do have a problem with ACBLScore's method (as I understand it) in which EW and NS are combined into one field without any arrow switches.
We had 17 tables today. Web Mitchell, three (I think, might have been two) sets of boards, 2 board rounds, 13 rounds, total 26 boards. Not "all play all" with only 13 rounds, but at least we all played the same boards. Two winners, neither of which were my partner and I.
As for tv, screw it. You aren't missing anything. -- Ken Berg
I have come to realise it is futile to expect or hope a regular club game will be run in accordance with the laws. -- Jillybean
#12
Posted 2012-December-04, 03:08
blackshoe, on 2012-December-03, 17:33, said:
But, for the purpose of producing a winner, the two-independent-sections movement has exactly the same problem. They may be the same deals in the sense of having the same cards in each slot, but if the matchpoints for a given result vary they're different boards.
I agree that there is a social advantage in having the same deals played in each section, but for comparison purposes it's definitely worse.
#13
Posted 2012-December-07, 01:27
gnasher, on 2012-December-04, 03:08, said:
I agree that there is a social advantage in having the same deals played in each section, but for comparison purposes it's definitely worse.
Seems to me the matchpoints depends on whether you have an even or odd number of tables. We were talking, as I recall, about dividing 18 tables into two nine table sections. Boards in either section will have the same top.
If you have, say, nine and eight tables, there are some movements that, iirc, will give you the same top in both sections. And then there's factoring. Not ideal, perhaps.
I would say I don't agree with your last statement, but more likely I just don't understand it.
As for tv, screw it. You aren't missing anything. -- Ken Berg
I have come to realise it is futile to expect or hope a regular club game will be run in accordance with the laws. -- Jillybean
#14
Posted 2012-December-07, 05:20
(1) Two sections, each playing a full Mitchell, with the same boards but matchpointed separately
(2) One section, playing half a Mitchell
The advantage of (1) is that the conversations in the bar afterwards will be more interesting. The advantage of (2) is that it's more likely to produce the right winner.
I'm not talking about the size of a top. With two sections, if EW in Section 1 are on average worse than EW in Section 2, NS in Section 1 have an unfair advantage over NS in Section 2. Effects like that are reduced by having a single section with an incomplete movement.
This post has been edited by gnasher: 2012-December-07, 05:26
#15
Posted 2012-December-07, 12:13
Yes, instead of "these 9 N-S get to play the weak pairs", you get "this one gets to play *all* the weak section, these two get to play 8-and-1 (and if that 1 is the weakest of the "strong" section, that isn't so bad), these two get to play 7-and-2, and so on. So maybe it's a bit mitigated. Of course, arrow-switching both sections would help there, as it does with the "oh my, there's no strong E-W pairs in this game" issue.
I do know that when I run two sections at the club, I will do a once-over the field to ensure that we don't have an overly-strong (or overly-weak) line; but when I run a 17, I'll do the same check to ensure there isn't a "murderer's row" that only half the field will have to handle all of.
But I haven't thought this through deeply; likely I'm missing something.
#16
Posted 2012-December-07, 14:26
gnasher, on 2012-December-07, 05:20, said:
(1) Two sections, each playing a full Mitchell, with the same boards but matchpointed separately
(2) One section, playing half a Mitchell
The advantage of (1) is that the conversations in the bar afterwards will be more interesting. The advantage of (2) is that it's more likely to produce the right winner.
I'm not talking about the size of a top. With two sections, if EW in Section 1 are on average worse than EW in Section 2, NS in Section 1 have an unfair advantage over NS in Section 2. Effects like that are reduced by having a single section with an incomplete movement.
Nobody around here holds conversations in the bar after the game any more.
Ideally, I think, you would seed all four fields, however many sections you have. One director here used to do that by putting a card on every fourth table that said "only A players here" or the equivalent. Of course, these days we get about half the NS's reserved for people with physical problems. It is true, IME, that if you let players randomly pick where to sit, or if you have a lot of relatively good players with physical problems, you end up with unbalanced fields.
Monday, we had "overalls" in our one section Web movement (17 tables, 26 boards, 13 rounds, 3 board sets). The EW pair who did best in that field got more masterpoints than the NS pair who did best in their field. There was no arrow switch. This makes no sense to me, but the program (ACBLScore) allows it, so the directors here assume it must be okay. I suppose it is, if your purpose is to give away masterpoints.
Heh. Another interesting thing that happened, irrelevant to this thread: there was a scoring correction, and new results were sent out. On one board, two NS pairs got 1430 for a shared top. However, one table played the board in 6S by NS making. The other, according to the report, played it in 5D by EW, down one. I'm told that the problem is that while it's easy to correct scores after the game in ACBLScore, that doesn't affect what the Bridgepad system thinks happened, correcting the Bridgepad data is difficult or impossible, and the contracts come from the bridgepads.
As for tv, screw it. You aren't missing anything. -- Ken Berg
I have come to realise it is futile to expect or hope a regular club game will be run in accordance with the laws. -- Jillybean
#17
Posted 2012-December-08, 03:54
#18
Posted 2012-December-08, 05:16
#19
Posted 2012-December-08, 11:24
As for tv, screw it. You aren't missing anything. -- Ken Berg
I have come to realise it is futile to expect or hope a regular club game will be run in accordance with the laws. -- Jillybean
#20
Posted 2012-December-08, 12:36