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Yorkshire
Chess Association |
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Grading
Calculation Examples |
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Consider a player who had a grade of 142 at the start of the season and has had the following 17 games from the latest season included in the grading system. (He may have played ones the grader knows nothing about. That is just unfortunate, not "wrong".) The points scored for each game are shown in the end column.
Game Res OppsGrade Points
1 ½ 128 128
2 1 156 206
3 1 128 178
4 0 [136] 86
5 1 130 180
6 ½ 156 156
7 1 128 178
8 0 158 108
9 1 116 166
10 1 100 152*
11 0 170 120
12 0 135 85
13 1 104 154
14 0 99 52*
15 1 94 152*
16 1 101 152*
17 1 102 152
-----Total points gained = 2405
Number of games graded = 17
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Note how in most games our player scored his opponent's score plus 50 for a win, scored his opponent's score less 50 for a loss, and scored his opponent's grade for a draw. Note that in game 4 the opponent had no grade. The 'working grade' calculated by the grader on all available data for that ungraded data was 136, and our player scored 136 less 50 for losing that game.
Note also that games 10, 14, 15, and 16 where against players graded over 40 points less our player's own grade of 142. Those opponents are treated above as though their grade was 40 points less than 142, i.e. 102. Thus in these games our player scored 152 (=102+50) points for a win, and scored 52 (=102-50) for a loss. If he'd drawn one of these games our player would have score 102 points for the draw.
A grade calculated over only 17 games is statistically approximate. If there were no grading record for our player from the previous two years then his grade would be 141 (2405 divided by 17) with a grade category of D.
Suppose, however, that our player had scored 2754 from 19 games in the previous season, and scored 3300 points from 24 games in the season before that. A further 13 games are needed to make up the latest season's 17 games to a total of 30. In this case games 13 are all 'borrowed' from the previous year. The points scored per borrowed game are 2754 divided by 19, so the total of points used for the 13 borrowed games is 2754 times 13 divided by 19, i.e. 1884. (If there had been only 9 games in the previous season then a further 4 would have been 'borrowed' from the season before that, to make up a total of 30.)
Our player's new grade is then calculated as follows. The total number of points is 2405 (from the latest season) plus 1884 (from the season before), and the total number of games is 30. 4289 points divided by 30 games gives a grade of 143, and the grade category will be C.