Main   Article 7Q42 by Richard Pavlicek  

Instant Matchpoints 1997

On Wednesday evening, September 17, players throughout ACBL-land will compete in the 11th annual Instant Matchpoint Pairs. Check with your local bridge club for the playing site nearest you. Don’t miss it!

Just what are “instant matchpoints” anyway? This article should provide some insight into this unique scoring method and the preparation behind it.

Most matchpoint events are scored by the actual results of each participant, i.e., each section (or group of sections) is matchpointed to determine the awards. An instant matchpoint event is different: The matchpoint awards for every possible result are predetermined. For example, if you bid and make 4 S, you will look up that score in a chart to find your matchpoint award immediately.

Which is better? On a strictly comparative basis, the regular method is superior because it is based on the actual results of the participants. But instant matchpoints are fun! Besides being able to find your score right away, these events are usually accompanied with written analyses. You can read about the deals you played and often gain tips to improve your game.

The most difficult task for an instant matchpoint game is to prepare the scoring awards. No matter how it is done, it cannot be completely fair because no one can predict the future; but it can approximate fairness. In virtually all cases the scoring awards are based on actual results when identical boards were played in a previous event. Of course, this event must have been foreign, and preferably long past, to minimize the chance of someone replaying boards that they remembered.

How are the matchpoint awards prepared? How can you determine an award for every possible result? I will explain the steps I follow using a hypothetical example. Assume Board 1 was previously played 180 times with the following data, which has been matchpointed in standard fashion to produce a 179 top:

N-S ScoreFrequencyMatchpoints
+9804177.5
+8003174
+4808168.5
+45026151.5
+42011581
+400620.5
-50179
-10010

The above matchpoints will not suffice on a general basis. What if a N-S pair scores +500, or -150, or any other result not shown? Well, you could refund their entry fee and tell them to try again next year — or you could adjust the table to account for gaps.

The method I use is to assume a “mystery score” is added to the original data, thereby increasing the top by one. Every existing score is presumed to have tied the mystery score, thus adding half a matchpoint to each; and every gap (including both end gaps) is matchpointed as if it were the mystery score. This produces the following table with a 180 top:

N-S ScoreFrequencyMatchpointsPercent
180100
+980417899
17698
+8003174.597
17396
+480816994
16592
+4502615284
13977
+42011581.545
+40062112
1810
-50179.55
11
-10010.50
00

Note how the top gap gets 180 (the new top) since it beats every real score, and the bottom gap gets zero. The gap between +420 and +400 would be worth 24 matchpoints, but there is no way to score +410 so it is eliminated from the table.

This method produces different tops on many boards, so for uniformity all awards are scaled to a 100 top, or percentage. Fractional percents are rounded to the nearest whole number. Oops! The award for -100 rounds to zero, just like the bottom gap. This is acceptable, but it feels wrong and is esoterically displeasing for different results to get the same award. Therefore I would smooth out the last three awards to be 2, 1 and 0.

As a final step, I occasionally adjust the matchpoints if I feel the results are biased by non-American systems, or if I feel our players would generally bid better. For example, suppose a successful North-South slam contract happens to earn 96 percent (giving the unlucky E-W victims a measly 4 percent) and I think the slam would be bid more often. I would back my judgment to lower the award slightly, including neighboring awards if also affected. I make these adjustments sparingly, and never by more than 10 percent.

Even with a protracted attempt to produce fair scoring awards, one cannot please everyone. So what else is new? Therefore, to eliminate potential bias, the ACBL goes one step further: The N-S and E-W fields are scored independently to produce two separate winners. Thus, if the awards on a board are biased to one direction or the other, it doesn’t matter. Everyone in your field is affected equally. TopMain

© 1997 Richard Pavlicek