After playing in the Teams events at the recent Peninsula Congress and the NSBC@Lindfield Restricted Congress, I thought I would try and understand and then explain how the extra report on the individual pairs performance is constructed.
I believe this explanation to be correct but there is almost no documentation out there on this so i am not certain about it. See these articles for some information about Teams scoring and VPs.
The results are shown from the perspective of one team (the Home Table).
When you look at the results for a team for a match for a board, in addition to the results at the two tables, there is an extra set of columns headed Pair Datums.
These show how the two pairs in the home table team each did compared to the other pairs in the field sitting in the same direction.
The Datum for a board is the average matchpoint score from all of the tables, excluding some top and bottom outliers (usually 1 pair of outliers if fewer than 11 tables, generally 10% of the results).
Then each pair separately is compared to the datum and the difference converted to Imps. This is known as Butler scoring. NB even when some outliers have been excluded, the remaining results can still be quite dispersed around the average.
The Pair Datums are not directly related to the team's results but are just an informal way for the pairs to compare themselves to their peers.
If you look at this board, (all scores are from the perspective of Team Wayland):
Table 1 Table 2
Contract Result Score Contract Result Score Net Score Net Imps Datum NS EW
5H S 10 -100 4HX S 10 -790 -890 -13 -210 3 -14
At table 1 (Wayland NS), NS bid 5H making 10 for a NS score of -100
At table 2 (Wayland EW), NS bid 4HX making 10 for an EW score of -790
The net score of team Wayland is -790 + -100 = -890, which is -13 Imps when converted.
The Datum score (IE the average score from most tables) is -210 for NS (+210 for EW). This reflects a mixture of good (game) scores and bad scores.
Wayland NS scored -100 which is 110 better than datum (-100 - -210) = +3 Imps pair score.
Wayland EW scored -790 which is 1000 worse than datum (-790 - +210) = -14 Imps pair score.
But from the team point of view, Team Wayland scored -13 Imps (not 3 - 14 = -11) for that board.
Note that +110 - 1000 = -890. Also, if the Datum data is blank, it means that the pair Imps were both 0 and the scores were the same as the Datum (±10).
The point is that you cannot derive the team's results from the component pairs' Imps results, they are measuring two different things.
We can illustrate this further by looking at the results from the NSBC event. Team Simmonds beat team Carter even though their EW pair, Eason/Hunter, didn't score particularly well as a pair.
You cannot simply add up the pairs' Imps (or the Imps Modified Datums) and compare them (Simmonds: 66 - 11 = 55 and Carter: 45 + 16 = 61) and conclude that team Carter won.
TEAM RESULTS
Place Team Imps VPs W‑D‑L
2 SIMMONDS 52 77.30 5-0-1
3 CARTER 50 73.32 4-0-2
By the way, masterpoints are usually awarded based on the number of matches won.
PAIR DATUMS
Rank Pair Imps Opp Avg Imps Modified Datum
3 SACHIKO CATHCART / J SIMMONDS 66 -4.0 64.1
4 SANDY CARTER / NERIDA GILLIES 45 -8.0 40.8
5 COLIN SPELLER / MAEVE DOYLE 16 12.0 22.1
10 SUSAN EASON / SIMON HUNTER -11 10.0 -5.9
In this Pair Datums report:
- Imps is the sum of the pair's Imps from the boards they played, calculated by comparing their scores to the datums. (EG from the example board above: -14 or +3). Eason/Hunter (EW) scored -11 overall; Cathcart/Simmonds (NS) scored +66 and were the third best pair.
- Opp Avg Imps is the average of the Imps achieved in their matches by the opponent pairs that the pair played against. Eason/Hunter's opponents' average Imps was +10 whereas Cathcart/Simmonds' opponents' average was -4. It is a measure of how well each pair's opponents played on the day.
- Imps Modified Datum appears to be the Imps adjusted by 50% of the Opp Avg Imps, IE is an attempt to adjust the Imps based on the strength of the opponents they played against. So Cathcart/Simmonds' modified datum is reduced (66 - 50% of 4 = 64.1), whereas Eason/Hunter's modified datum is better than their Imps (-11 + 5 = -5.9).
My conclusion here is that the stronger (better scoring) players were generally sitting NS (including Carter/Gillies) and so generally were playing lower scoring EW pairs.
If you are having trouble grasping all of this, you are not alone!
