Power Ratings Home Page

 

Goal of Power Ratings

 

            To bracket/strat/flight all events so that pairs and teams of similar skill levels are competing against each other.  Masterpoints does a pretty good job of this.  2 out of 3 times a pair or team will get into the correct bracket/strat/flight.  But we should not be satisfied with this.

 

Bowling Average

 

            When I bowled, no one ever asked me what the total number of pins I knocked down was, but a lot of bowlers wanted to know what my average was.  Master Points is the total number of pins.  Power Ratings is the bowling average.

 

What is a Pair Rating

 

            Pair Ratings are the strongest rating for a partnership.  It is the pair’s average game percentage adjusted by their degree of difficulty.

 

What is a Degree of Difficulty (DOD)

 

            For each game, add up the ratings for your opposition (the players sitting your direction in your section and other sections if scoring across the field) and divide by the number of players. Subtract 50 from this result to find your DOD.  Let’s say that your average competitor has a rating of 53, and you and your partner have a game percentage of 52%.  You must be better than your competition that has a rating of 53.  So add your DOD, 3, to your game percentage, 52, to get a pair rating of 55 for you and your partner.

 

What is a Power Rating (PR)

 

            Everyone has a rating. Your rating for each game starts with your game %.  Your opposition’s strength is factored out. Then your partner’s strength is factored out.  What is left is how well you score at bridge, or your rating. 

 

Your rating becomes a Power Rating, and you become a rated player, when you have played 11 match point pair games with rated players other than your favorite rated partner, during the past 24 months.

 

            A rating is your average game % when you are your own partner and you compete against average players.

 

            Your rating for each game is your % plus DOD, split between you and your partner, then doubled.  This % plus DOD is split between you and your partner using the same ratio as your overall rating to your partner’s rating.

 

            For instance, if your rating is 60 and your partner’s rating is 40, you will have a 3 to 2 (60/40) split.  From your % plus DOD (55) you get 33 and your partner gets 22.  These numbers are doubled.  Your rating for this game, 66 is higher than your overall rating, 60.  If you have 100 games, your rating goes up 1/100th of 6, or 0.06.  Your new rating is 60.06, and your partners new rating is 40.04.  If your rating goes up, your partner’s rating goes up. If yours goes down, your partner’s go down.

 

Other things that affect your rating

 

               At the end of the month, your games from 24 months ago go away.  If you have a personal summary, it will tell you how many games and the average rating of those games.  On the right side, after your rated games for last month, you will see something like “52.28 PR for 24 games in May 2016”. These games are in your rating now, but they will go away after the end of this month.

 

               Each time the website is updated, everyone’s rating is updated.  Every game, during the past 24 months, is recalculated.  The % stays the same, but the DOD’s change slightly, based on your oppositions new ratings.  Your split with each partner changes based on you and your partner’s new ratings.

 

               Yes, it is possible to have good games and see your rating drop.

 

How to find your personal summary

 

Under “Unit Races” on the home page, select “Other Units”.  Then select your unit.  Now you will be in your Unit’s home page. Select “Power Ratings” and you will be taken to your Unit’s Power Ratings leader board.  If there is a yellow box at the top of the leader board, you may be able to find your name.  If your name is not listed, contact me at ckchampion@netzero.net, and I will be happy to add your name.  After you select your name you will see your summary.  The left side of the screen shows a summary of your partners during the past 24 months.  Your games with the partners near the top of the page have exceeded your and your partner’s power ratings.  Your average game percentage with that partner has been divided between you and your partner using a ratio equal to your and your partner’s overall power ratings.  The partners near the bottom, well someone, you or your partner, has not been playing up to their average level of play.  It is no prediction of your future games, just a recap of what has happened during the past 24 months.  The right side of your summary is devoted to individual games played during the past 4 months. 

 

Most underrated KO teams

 

               When I suspended KO Power Ratings, I tried replacing them with actual KO results.  This did not work because comparing the W/L record of teams in bracket 1 with teams in other brackets is like comparing apples and oranges.  Instead I chose to prove/disprove the validity of Power Ratings.  If teams flagged as underrated had W/L records both above and below 50%, then Power Ratings would fail as often as they worked.  The teams shown here are selected based on underrate (UR), not their W/L record.

               KO’s should be bracketed so that all teams in a bracket have about the same chance of winning.  This test is designed to show which teams win far more often than the average team, and which teams virtually never win their bracket.

 

Master Point to Power Ratings conversion chart

 

               This chart is the average Power Ratings for players in these Master Point ranges.  If you want the average Power Rating for 5000 Master Points, it is the low end of the Power Rating range corresponding to 5000 to 10000 Master Points.  For 7500 Master Points, the average Power Rating is the exact middle of the corresponding Power Rating range.

 

Games Stratified by Power Ratings

 

               The game files include Strats based on Pair Ratings first, Power Ratings second, Master Points last.  At the end of each line, the first character is the Strat assigned at game time.  The second character is the Strat assigned by Power Ratings.  The last number is the actual rating used to calculate the Power Rating Strat.  Strat A is the top 3rd of the field.  B middle 3rd. C bottom 3rd.  If a Pair Rating exists for that pair, it is used.  Otherwise each player’s Power Rating is used.  If a player has neither, then a Power Rating is computed using the Master Point to Power Rating conversion chart.

 

What is wrong with the Master Point rating system?

 

            Every time you play, your rating goes up or it stays the same, no matter how poorly you do.  Many members feel bridge players would object to seeing their rating go down.  Instead we insist that players play in the highest strat or bracket if they have that many Master Points.  They and their partners/teammates may feel they have very little chance of winning.  As a result, many of these players stop participating.  I feel it is better to lower their rating so they can play in a bracket or strat where they are competitive.  I think they will come back.

 

            When stratifying events, Power Ratings will look at both players in a partnership.  If a Pair Rating is found, that is used.  If not, but Power Ratings are found, that is used.  If one or both partners have neither, then Master Points are used for the player(s) with no Power Rating.  Only players that rarely play will have neither.  The level of play for that partnership will determine the strat.

 

Tight brackets

 

            I often hear players say they like to play KO’s in Gatlinburg because the brackets are so tight.  The only thing tight about these brackets is the number of Master Points for team in a bracket.  The level of play can vary widely within a bracket.  If KO’s were bracketed by Power Ratings, then all teams in a bracket would have about the same level of play, but their Master Point totals would vary widely.

 

What is the purpose of Power Ratings?

 

               The Master Point Rating system is a great system for awarding exceptional play, but a poor rating system.  It should be renamed the Master Point Awards System.

 

               Power Ratings is a rating system based on a bridge player’s scoring ability today.

 

               Bridge events should be bracketed/stratified so that all teams/pairs within a bracket/strat have close to the same skill level and chance of winning.

 

               We need to keep Master Points as rewards for winning events.  However using Master Points to push players into ever higher brackets/strats is a disincentive.  Better to use Master Points to measure a player’s ability during their bridge career, and use Power Ratings to measure a player’s ability today.

 

A rating system based on performance is a long way off.  Until then, Power Ratings is a tool to gage your chances of winning.  This is based on your performance compared to your Master Points.  Power Ratings will estimate you and your partner’s average game percentage.  You will need to supply the type of event you will play in.  Power Ratings will estimate your KO team’s won loss match percentage.  Click here:

 

 

PR Predicts

 

How Power Ratings protects your privacy

 

You can hide your personal summary.  Send me an email and I will send you a secret link to your Personal summary.  The game data used to compute Power Ratings is readily available on the internet.  If you want your name, and personal summary, removed from Power Ratings, I will be happy to do this.  Send me an email at ckchampion@netzero.net.

 

How to include your club games (club owners only)

 

·  You need ACBLscore. Almost all clubs use this to score their games.

 

  This looks daunting, but once you learn it, it will seem as easy as creating the monthly reports for the ACBL.

 

  1) start ACBLscor

  2) From the menu (top line) select "Utilities"

  3) Select "Backup/Restore"

  4) Select "2 Backup Game Files"

  5) Backup Location: "c:\acblscor\gamefile"

  6) Enter game files to backup.  Type in "1408??" for Aug, 2014 or "14????" for all of 2014 or"??????" for all games

 

  the file name will be 1408xx.lzh or 14xxxx.lzh or xxxxxx.lzh, and found in "c:\acblscor\gamefile"

 

  Please attach this file to an e-mail and send to me at

 

  ckchampion@netzero.net

 

I can use up to two years worth of games, but I will use any amount of games you send. I update each month. The best time to send me your new games is the same time you e_mail your reports to ACBL.

 

You are done, but if you need more help with browse buttons and attachments:

 

 

 

 

Browse button:

 

  1) From ACBLscor, after step 4 "2 Backup Game Files"

 

click on the browse button

 

Desktop is at the top.  Click on it.

 

  or

 

  You can expand a different location by clicking on the icon

to the left of the location.  You can continue expanding locations

within each location by clicking on the icon to the left of

the sub location.  For example "ACBLSCOR" and then "GAMEFILE".

When you find the location you want, click on it, not the icon to

the left, and click on the "OK" button.

 

 

 

 

  2) from your email account "attaching the backup gamefile"

 

select attach or attachments

 

you should see a browse button.  Click on it.

 

you should see a list of locations on the left.

 

  a) if you see "Desktop" and that is where you put the backup gamefile:

 

     click on it and find "1107XX.lzh" in the list on the right side.

     click on it and click on the "open" button or the "OK" button.

     click on "attach" and "finish" or whatever you have to do to

   complete the attachment process in your email account. 

     send email to me.

 

  b) if you do not see "Desktop" or you put the backup gamefile

somewhere else click on the "Folders" button

 

     Click on the icon to the left of "Desktop"

     Click on the icon to the left of "Computer"

     Click on the icon to the left of your hard drive "C:"

     Click on the icon to the left of your high level folder "ACBLSCOR"

     when you get to the last folder "GAMEFILE" click on it, not the icon

   to the left, and find  "1107XX.LZH" in the list of files on the right.

     Click on the "open" or "OK" button.

     click on "attach" and "finish" or whatever you have to do to

   complete the attachment process in your email account. 

     send email to me.

 

Any questions please contact me.

 

ckchampion@netzero.net

Chris