Big Step Forward for X-Clubs ... and Bridge in New Zealand

Bob Fearn, as many will know, is the author of Compass scoring which is the engine powering X-Clubs and, for the last four years, the NZ-Wide Babich Simultaneous Pairs. In 2018 Bob took an interest in scoping out a National Grading System (NGS) for use in New Zealand. An NZB NGS would open up a whole new dimension to our game - handicaps. Bridge players can now go out to beat their handicap not their playmates. This challenge is now available for all players of X-Club deals.

Bob completed this massive project using the X-Clubs data-set as a basis. In effect all players of X-Club hands will earn an X-Clubs rating. Let's call it XG because it's a closed shop based on C-point club bridge played with the same hands - a very different situation from a true NGS which would include both club and tournament results and, for about two thirds of clubs, no comparison based on the same cards being played. XG ratings open the door for NZ bridge to provide large-scale handicapped results.

Calculating everyone's XG involves a huge amount of data crunching which happens weekly so that any score changes get incorporated. The method closely parallels the EBU model and involves consideration of your XG, your partners' XG's, and the combined XG's of all your opponents for your week's bridge just gone. XG's are calculated over the most recent 2000 boards before old scores begin dropping off. More recent scores get a higher weighting than older ones. A minimum of 300 boards - about 12 sessions - need to be played before an XG starts to settle down - see the graph below. A basic example of how the calculation is done is attached below. Click to download it.

Starting from Week 04 in 2019 a complete summary of over 3500 X-Clubbers has been posted along with the weekly Leagues tables.

Every result Ladder - two per day - comes with sortable columns - especially XG Rating, XG Handicap Result, XG Handicap Placing, XG Status. An example:

Just click on any of the green column headers to sort as desired - example

The three categories of XG Status U, E, M are Unpublished (played < 150 boards), Evolving (played between 150 and 1000 boards) and Mature (played > 1000 boards). This is because it takes a while for the XG's to settle down - see graph below as an example. Thus, a reasonable player who is status U has a good chance at coming top on the Handicap as their XG will be assigned by defaults based on NZB Rank ... until they get beyond 6-7 X-Club sessions.

Remember .. all the columns in the Ladder may be sorted by clicking on the green column headers.

Sample GraphSample Graph

At present there are no plans to provide an interface to a tabulation like this although something similar should be made available to players should NZB develop its own NGS. Bob's utility can export an individual's record to Excel (sample attached below), produce a graph, or export a summary of everyone's standings to Excel.

Separate handicapped results ladders are now published for each X-Clubs session.

NOW - the Main Course: Bob has moved beyond what we understand any other scoring system to have done. By applying the same methodology as used in the weekly recalculation of everyone's XG rating, Compass clubs (and soon NZ Scorer clubs too, we have heard) can now generate handicaps tailored to each session after the raw results are known. Starting with the average of each pairs' XG's and modifying that for the Strength of their opponents we can now come up with a balanced set of handicaps to apply to the raw results. An indication that this is a fair and equitable method of handicapping is the fact that the sum of all handicaps in the field is always zero. That the weightings applied balance out to a net zero sum is mathematically provable. Compass clubs need only specify the Handicap List as List 19 in the Club Calendar of Events (or choose to select a different handicap list under Edit Options when viewing the session) for these new Dynamic Handicaps to be applied.

Further .. for non-Compass clubs playing X-Club deals Bob is thoughtfully providing weekly text file updates of their members' latest XG ratings so that those clubs too have the basis to enjoy the new Dynamic Handicapping facility. Dynamic handicaps must surely form the basis of any NZB handicapping system once NZB starts producing its own National Grades. Meanwhile ... it's just X-Clubs clubs that have access to this fantastic new facility.

Non-X-Clubbers .. are you up for battling your handicap? Talk to your committee today about giving X-Clubs a try. It's free. It's easy. Join the 40 other NZ clubs that play the same hands simultaneously every day.

XG - A practical example.doc32.5 KB
XG Record for 64504 Michael Neels.xls68.5 KB