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The Ratings Process
USA Table Tennis' active members are rated to determine event eligibility and to help prepare proper draws. The rating system works like this: following a USATT sanctioned event, the tournament director sends the results of the tournament in to USATT headquarters. There, the USATT Ratings Coordinator processes the results using the tools under the Ratings option from the main menu of the IMS.
The following steps are then performed:
Each step is the subject of a section below.
The Tournament Report
Then, the fact that the results have been sent to headquarters is entered into the tournament report dialog (Ratings Menu). At the same time, the fees for player ratings are entered into the database.
Entering the Player List
Then, each player who participated in the tournament is selected from the membership/ratings database. This is done using the Player list selector (press the button marked Players). Players can be selected by scrolling through each record, or by entering their membership ID, or their name. If a player is not found in the database, they must be entered as a new member to continue processing. This is done via the Membership Menu.
Entering the Match List
When the player list is complete, entry of each match begins (press the button marked Matches). A player's name is highlighted in the Player list box, and the Winner or Loser button is selected. The Event name and the scores may be entered. When a winner and a loser have been selected, the Add button can be pressed to add the match to the list at the lower right. When all matches have been entered, the OK button is used to save the match list. Scores should be entered for matches that involve unrated players. As each match with a score is entered, the program looks at the match score, and using an inverted handicap chart, estimates what the rating difference between the two players should be. This information can be used by the Ratings Coordinator to help determine an initial rating for an unrated player.
When to Process a Tournament
When all players and matches are entered, it might be time to calculate the new ratings. Why isn't it time to process it now? Because all tournaments must be processed in the order that they are played. The Information Management System makes sure that all tournaments are processed in order. Any tournament director who doesn't send in his results in a speedy fashion can gum up the works. The IMS was designed to allow player and match list entry as soon as the information was available, and holding this information in an unprocessed form until all previous tournaments were processed.
If a tournament report is late (not received by 10 days after the tournament), call the tournament director. If it's very late, call the regional tournament coordinator.
Basics of the Rating System
A Note About
If you look at the
individual rating reports on the rating-history
pages, you will sometimes notice a player who gains
more than 50 points but whose rating is not adjusted. The reason for this is
that the rating system makes four passes:
Pass 1: Temporarily
adjust rated players.
Pass 2: Give initial
ratings to unrated players.
Pass 3: Determine
adjusted ratings using initial ratings for rated players and the ratings from
Pass 2 for unrated players..
Pass 4: Calculate
final ratings using the ratings from Passes 2 and 3.
rating report only shows the points gained per match in Pass 4. Since the rating
of a player's opponent in Pass 4 may have been adjusted in Pass 3, the player
can gain over 50 points in Pass 4 even though in Pass 3 he did not exceed the
50-point threshold required to get an adjustment.
Note that the
ratings are calculated by the USATT’s Information Management System, not by
hand, so it is unlikely that there is a numerical error in your rating.
USA Table Tennis Rating Chart
|Point Spread Between Players||Expected Result (Higher Rated Player Wins: number of points exchanged)||Upset Result (Lower Rated Player Wins: number of points exchanged)|
|0 - 12||8||8|
|13 - 37||7||10|
|38 - 62||6||13|
|63 - 87||5||16|
|88 - 112||4||20|
|113 - 137||3||25|
|138 - 162||2||30|
|163 - 187||2||35|
|188 - 212||1||40|
|213 - 237||1||45|
|238 and up||0||50|
For example if player A (rated 1814) defeats player B (rated 1800), player A will gain 7 points (becoming 1821), and player B will lose 7 points (becoming 1793). Players who have not played in previous USATT tournaments will be given an initial rating based on their performance in their first tournament. Additionally, players with exceptional gains following a given tournament may be given an adjusted rating. In addition to rewarding the adjusted player for his performance, this also reduces the rating losses sustained by his opponents.
The process is performed in 4 passes. They are described below.
Pass 1 - take all rated players, and check for probable adjusted players
Start each rated player from their pre-tournament rating. For each match against another rated player, use the ratings chart to determine the change in rating points. If a player's rating goes down, or up by less than 51 points, their rating for pass 2 is set to their pre-tournament rating. If a player's rating went up by 51-75 points, their rating for pass 2 was set to their rating after pass 1. If a player's rating went up by more than 75 points (and they had at least one loss), their rating was calculated from the following:
This is an average between their pass 1 result, and the average of the player's BestWin (the rating of the highest rated opponent that the player defeated) and the player's WorstLoss (the rating of the lowest rated opponent that the player lost to).
Pass 2 - take all unrated players, and attempt to set a rating
For each unrated player, try and find an initial rating using the following formula:
The ratings for rated players are the Pass_2_ratings given above. No points are given/taken away for matches against other unrated players at this point. In addition to the rating, a rough measure of the quality of the rating is presented using the following formula:
If we assume that the player's best win was against a 1640 player, and his worst loss against a 1660 player, this sets Initial_Rating = 1650, and Confidence = 99%. Confidence numbers below about 95% should be checked by looking at match scores. Confidence numbers below 75% imply a 500 point difference between BestWin and WorstLoss, and the program will simply set Initial_Rating = 0.
A second method to get an initial rating is done through inverting a handicap chart. For each of a player's matches, look at the scores, and determine the handicap that would have brought the game to deuce. Then, use the handicap table to find the rating difference that gets that handicap. Add (if the unrated player won the match) or subtract (if he lost) that rating difference from the opponent's pass 2 rating. This gets an estimated rating based on that match. Repeat for all matches, then average all the estimated ratings together.
In general, players who only play other unrated players are very difficult to rate. Players who don't win matches are very difficult to rate. Generally, players (especially beginners) who haveratings below 700 either quit or improve - sooner or later, their ratings will reflect their standing amidst the playing community. Improvements are often so quick that their beginning ratings are nearly discarded via the adjustment system.
Pass 3 - take all players and check for required adjustments
All previously rated players start from their pre-tournament rating. Unrated players start from their initial rating given in pass 2. For each match, calculate the change in rating points from the standard rating chart. If a player's rating goes up by less than 50 points, their rating for the final pass is set to the same as their pre-tournament rating. If a player's rating goes up by 50-75 points, their rating for the final pass is set to their rating after pass 3. If a player's rating goes up by more than 75 points (and they had at least one loss), their rating is calculated from the following:
This is an average between their pass 3 result, and the average of the player's BestWin (the rating of the highest rated opponent that the player defeated) and the player's WorstLoss (the rating of the lowest rated opponent that the player lost to).
Pass 4 - Final Pass
The ratings for adjusted players from round 3 (which might include formerly unrated players), and initial ratings for unrated players (who didn't need an adjustment) from round 2, are combined with the rest of the players who did not need an adjustment. For each player, and each match, we go through the rating table process. This results in the final rating.
Updating the Ratings
Following the four pass ratings system, the Ratings Coordinator should review the ratings summary files for accuracy. These are saved to the #.IDV and #.SUM files (replace # with the tournament ID). If no errors are noted, then it is time to update the ratings database. This is done by pressing the Update button on the tournament processing dialog box.
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