Main     Article 7Q41 by Richard Pavlicek    

Instant Matchpoints 1993

Did you ever wonder how instant matchpoints are obtained? Let me rest your anxiety. They come from the Dart Room at ACBL Headquarters. Prior to every tournament an employee throws hundreds of darts at a huge wall chart, thus determining the matchpoints for each possible result.

Just kidding. Instant matchpoints are determined by the frequencies of actual results when the deals were played in a previous tournament. Of course, the tournament must be foreign (and preferably not recent) so the chance of anyone having played and recognizing the deals is remote.

For the last seven years I have done the analyses and prepared the matchpoint tables for the ACBL Instant Matchpoint Pairs (usually sponsored by Royal Viking Line). I receive a list of frequencies for the results on each board. To illustrate the process, say Board 1 was played 16 times with these results:

N-S ScoreFrequency
+4502
+4204
+4003
+1706
-501

Matchpointing on a 15 top produces:

N-S ScoreFrequencyMatchpoints
+450214.5
+420411.5
+40038
+17063.5
-5010

This is easy so far, but what about scores that are not listed? For example, what should a score of plus 430 receive? Obviously it should be between 11.5 and 14.5, but what exactly? Or, worse yet, how about a score of minus 100! Since minus 50 gets a zero, is there anything worse?

There are a number of ways to do this. The simplest and most elegant is to imagine a “mystery result” being added to the data, increasing the top by one. Each actual result is matchpointed as if it had tied the mystery result, and each gap is matchpointed directly as if it were the mystery result.

The following table shows this adjustment from a 15 top to a 16 top with all gaps properly matchpointed.

N-S ScoreFrequencyMatchpointsPercent
16100
+45021594
1488
+42041275
+40038.553
744
+1706425
16
-5010.53
00

Note that the effect is to increase all existing matchpoints by a half. Also note that the gap score between +420 and +400 is omitted because it is impossible to score +410. In theory this gap would receive 10 matchpoints; but who cares!

The final column shows the matchpoints converted to a percentage (as if 100 were top). All percentages are rounded to the nearest whole percent.

To illustrate the methods, I have greatly reduced the amount of data. Typically, each board has hundreds of results, so the adjustment to a 100 top is actually a reduction from some huge actual top. I wrote a short computer program to do all the calculations (else I would definitely prefer the Dart Room).

Do I edit the matchpoints in any way? Yes. When two (or more) results yield the same matchpoint score, I either combine them into a single gap or adjust one (plus or minus 1) so the scores are different. I also remove ridiculous results — you know, like the guy who goes for 1400 on a partscore deal.

Lastly, when analyzing the deals, I occasionally make minor adjustments if I feel the matchpoints wrongly reflect what would happen at an American tournament. For example, suppose a laydown slam receives 95 matchpoints, yet I feel it should be reached by sound standard bidding. Clearly, this is an injustice (especially to the opponents) so I would make appropriate adjustments (including neighboring scores) to lower it to, say, 87 matchpoints.

Sometimes I would like to make drastic changes (such as lowering my preceding example to 65 matchpoints) but I resist the temptation. One must not forget that the frequencies are based on facts, and it’s not nice to fool with Mother Nature.

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© 1993 Richard Pavlicek