Grading Calculation - New Players with 0% or 100% Scores

[Ian Thompson]

Can anyone tell me how the grading system calculates ungraded players grades when they have either lost all their games or won all their games (so all you can reliably say is that they are either significantly weaker than all the players they have lost to, or significantly stronger than all the players they have beaten).

What would the calculation be for these two examples:

1. New player loses 10 games to opponents all graded 150
2. New player wins 10 games against opponents all graded 150

In a slightly less extreme example, what would the calculation be for:

1. New player loses 10 games to opponents all graded 150 and wins 1 game against an opponent graded 50
2. New player wins 10 games against opponents all graded 150 and loses 1 game against an opponent graded 250

[Greg Breed]

What would the calculation be for these two examples:

1. New player loses 10 games to opponents all graded 150
10*((150-90)/10)=60
2. New player wins 10 games against opponents all graded 150
10*((150+90)/10)=240

In a slightly less extreme example, what would the calculation be for:

1. New player loses 10 games to opponents all graded 150 and wins 1 game against an opponent graded 50
(150-90)=60*10=(600+90)/11=63
2. New player wins 10 games against opponents all graded 150 and loses 1 game against an opponent graded 250
(150+90)=240*10=(2400+0)/11=218

Something like that...

[John Upham]

The conclusion I draw from this is that if one is able to beat strong rated players then is much better to do this whilst unrated.

If you do this with a rating then one is limited by ones current rating.

The same set of results will obtain a different rating.

Is anyone able to provide a non-mathematical rationale of this?

[Ian Thompson]

What would the calculation be for these two examples:

1. New player loses 10 games to opponents all graded 150
10*((150-90)/10)=60
2. New player wins 10 games against opponents all graded 150
10*((150+90)/10)=240

In a slightly less extreme example, what would the calculation be for:

1. New player loses 10 games to opponents all graded 150 and wins 1 game against an opponent graded 50
(150-90)=60*10=(600+90)/11=63
2. New player wins 10 games against opponents all graded 150 and loses 1 game against an opponent graded 250
(150+90)=240*10=(2400+0)/11=218

Something like that...

Thanks for this. I was hoping to get a definitive answer from someone on the ECF grading team. | thought the grading system did an iterative calculation which re-estimated an ungraded player's grade until such time as the estimate equalled the performance. In all these cases, that approach won't work. It's obvious for the players who have lost all their games or won all their games that the grades would be minus infinity and plus infinity. Its perhaps less obvious that the same applies to the players who have one win/one loss. Application of the 40 point rule means that the equations you need to solve have no solution.

[Howard Grist]

The first step of the grading process is to calculate an 'initial grade' for new players. This is done in two stages. The first is an iteration using 40 points for a win and ignoring the 40 point rule. The second stage is to use the result of the first stage as the new player's grade and grade his results using 50 points for a win and the 40 point rule. The new player is then treated as a graded player with a grade given by the 'initial grade'.

So, to answer the questions actually asked:-

1. New player loses 10 games to opponents all graded 150
Initial grade Stage 1 gives: 10 x (150 - 40) / 10 = 110
Initial grade Stage 2 gives: 10 x (150 - 50) / 10 = 100
Published grade: 10 x (140 - 50) / 10 = 90

2. New player wins 10 games against opponents all graded 150
Initial grade Stage 1 gives: 10 x (150 + 40) / 10 = 190
Initial grade Stage 2 gives: 10 x (150 + 50) / 10 = 200
Published grade: 10 x (160 + 50) / 10 = 210

1. New player loses 10 games to opponents all graded 150 and wins 1 game against an opponent graded 50
Initial grade Stage 1 gives: (10 x (150 - 40) + (50 + 40)) / 11 = 108
Initial grade Stage 2 gives: (10 x (148 - 50) + (68 + 50)) / 11 = 100
Published grade: ((10 x (140 - 50) + (60 + 50)) / 11 = 92

2. New player wins 10 games against opponents all graded 150 and loses 1 game against an opponent graded 250
Initial grade Stage 1 gives: (10 x (150 + 40) + (250 - 40)) / 11 = 192
Initial grade Stage 2 gives: (10 x (150 + 50) + (232 - 50)) / 11 = 200
Published grade: ((10 x (160 + 50) + (240 - 50)) / 11 = 208