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31 Aug 2020 - 3:00pm

In the results list, why do pairs with the same matchpoint totals sometimes have different percentages?

This often happens when a board has an artificial score (for example, AVE). The pairs who played the board are matchpointed against each other, excluding the artificial scores; these matchpoints need to be weighted.

 

How is the percentage calculated for a session without any artificial scores, and for pairs with exactly one artificial score?

To get the percentage from the matchpoints, the formula is:

% = Mps/(Bds*Top) 

where

  • Mps = Matchpoints earned in the session
  • Top = Number of results per board minus 1
  • Bds = Number of boards

How is the percentage calculated for a session with an artificial score at a single table (for pairs without an artificial score)?

To get the percentage from the matchpoints, the formula is

% = (Mps-BdMps+(BdMps*Top/(Top-1))/(Bds*Top)

where

  • BdMps = matchpoints on the board with an assigned score

What is an example?

Consider a 10-table. 24-board session, with a Mitchell movement, where on one board, Pairs A and B were assigned an AVE. On this board, Pair C earned 1 matchpoint and Pair D earned 6 matchpoints. Both pairs had a total of 113.5 matchpoints for the 24 boards, but the results show them with different percentages. Percentages for the other 16 pairs in the event can be calculated in the manner of pairs C and D

Pair A 68.00 31.48 68/(24*9)
Pair B 140.00 64.81 140/(24*9)
Pair C 113.50 52.60 (113.5-1+(1*9/8))/(24*9)
Pair D 113.50 52.89 (113.5-6+(6*9/8))/(24*9)

 

How does it work in the general case, with multiple artificial scores on multiple boards?

For all players who play a factored board their score on that board is multiplied by Top/(Top-N)
For all players who do not play that board their artificial score on that board is multiplied by Top/(Top-N+1)
All other scores are left as is

  • N = Number of artificial results on that board

 

Concept from Will Watson; errors by submitter

27 Jul 2020

  Monday, July 27th

  • 12:10 pm 499er (Sunset)
  • 12:20 pm Open (Sunset) 
  • 6:45 pm, 299er (Quicktricks)
  • 6:45 pm Open (Quicktricks)

Tuesday, July 28th 

  • 12:30 pm 499er (SF Bridge Center at St. Mary's)
  • 1245 pm Open (SF Bridge Center at St. Mary's)

Wednesday, July 29th

  • 12:10 pm 499er (Sunset)
  • 12:20 pm Open (Sunset) 
  • 6:45 pm Open (Cardology)

Thursday, July 30th  

  • 10:30 am 199er (PIPS)
  • 11:45 pm 499er (PIPS)
  • 12:35 pm Open (PIPS)
  • 3:00 pm 299er (PIPS)

Friday, July 31st

  • 12:10 pm 499er (Sunset)
  • 12:20 pm Open (Sunset) 

Saturday, August 1st  

  • 12:15 pm, Open (Cardology)

Sunday, August 2nd

  • 1:10 pm Open (SF Bridge Center at St Mary's)

All the individual clubs in Unit 506 are offering ACBL Virtual Club games on Bridgebase.com at similar times as their regular club games.  See Home for schedule.  See Local Clubs for the contact person for each game.

In light of the shelter-in-place orders, the April and May 2020 Unit Games and regular club games, and the SF Summer Sectional (previously set for June 2020) have been cancelled.

 

Pictured above is a training session for prospective Handz teachers (from left to right are current and prospective Handz teachers: Deborah Drysdale, David Achterkirchen, Handz creator Richard Bellerose, and Michael Levin)