Percentages
Below are the results from a session of bridge.
Each pair has a percentage score on the right-hand side, which is obviously their score for the night. But how are these percentages earned ?
Each board is played at different tables over the course of the session.
Here are the eight results from board 6 :
We see the names of the N-S pair and E-W pair, the Contract, and the result as an EW Score. All the contracts were played by West, all the contracts were successful, all the scores are in the EW column.
The only difference between the scores is whether game was bid or not, and how many tricks were made by each West player.
On the first line West bid game and made 10 tricks, scoring 620.
On the second line West made 10 tricks but they didn't bid game, so they only score 170.
On the third line they didn't bid game, made the 9 tricks they bid, and so scored 140.
etc
We now RANK all of these eight scores from top to bottom.
The top score is 650, then 620, then all of the 170 scores are third equal, and the 140 score is last or bottom.
650 1st EW
620 2nd EW
170 3rd equal
170
170
170
170
140 8th EW
This ranking is reflected in the next two columns - NS MP and EW MP.
MP stands for MatchPoints. It is just a number the computer calculates to give a score to each pair based on the ranking of their result on this board. Here the top score of 650 gets an MP score of 14, 620 gets 12, all the 170 scores get 6, and the 140 gets zero MPs.
The NS pairs get the opposite score.
So, the NS pair who had 650 scored against them are bottom and get zero MPs. The NS pair who had 140 scored against them are top and get 14 MPs. The two sides all add to 14.
As a Percentage
After you play a board the tablets show a percentage. This is just the number of Matchpoints gained, divided by the top MP score.
650 here scores 14/14 = 100%.
620 scores 12/14 = 85.7%
170 scores 6/14 = 42.8%
140 = 0/14 = 0.00%
At the end of the night, when all results are in the system, the computer takes each pair's percentages on each board and averages them, giving the overall percentage score.
(The computer actually does the calculations in MPs because some boards may not be played as many times as other boards, and some pairs may be phantom for a round and have no score on a couple of boards.)
When you see a percentage result on the tablet, it is only the result so far. As more results come in the percentage for your score will change.
So early in the session the percentage doesn't mean much, but after a couple of hours it will be fairly representative of the final result.
Analysis
You can review the results on each board and come to some conclusions about what happened, who was skillful or not.
Here are the hands for Board 6, and also the Makeable contracts.
So, we can see that EW only had 18 combined points, but a big heart fit.
11 tricks are makeable with hearts as trumps (5H).
So the pair that bid 4H and made 11 tricks made the maximum available.
All the other Wests didn't make as many tricks as they could have. You need to finesse twice in diamonds to pitch a loser in spades or clubs. The diamond lead certainly helped the player who made 11 tricks. So 10 tricks is probably "normal".
Most pairs didn't bid the Game. I suspect most West's opened 3H and East failed to raise to 4H, but they should. Maybe North doubled and pushed East into bidding 4H.
So, the next day you and partner can go through every board, looking at your results and thinking about what you could have done differently. Sometimes one of you is at fault, sometimes the opposition make a great bid or play, and sometimes it's just bad luck.
Here are some more boards from the same session.