Originally posted by emanonThey'd both stay at the same rating.
Two players with equal rating (assume their strength is exactly the same, indefinately) keep playing each other and keep drawing since neither of them can win (or lose). Question: Will their rating keep increasing, indefinately? Just wondering...
Players are rated using the following formula:
New Rating = Old Rating + K * (Score - Win Expectancy)
K is a constant (32 for 0-2099, 24 for 2100-2399, 16 for 2400 and above)
Score is 1 for a win, 0.5 for a draw and 0 for a loss.
The Win Expectancy is calculated using the following formula :
Win Expectancy = 1 / (10^((OpponentRating-YourRating)/400)+1)
The Win Expectancy is used in the rating calculation but is interesting on its own. For example, the calculation below is for a rating difference of 200. This shows that if you have a rating 200 points higher than another player, you can expect to beat them, on average, three times for each four games played.
Win Expectancy = 1 / (10^(-200/400)+1) = 0.76
Note: ^ = "to the power of", e.g. 2^3=8.
If you have a non-provisional rating and you play a provisional-rated player, then you receive (or lose) only half the number of rating points you would normally. If the provisionally-rated player has played fewer than five games, then their rating is treated as 1200 when calculating your rating.
http://www.playtheimmortalgame.com/help/index.php?help=faq
Originally posted by AThousandYoungSomebody put me out of my misery. I am not a complete mathetmatical idiot, but this equation seems to predict a small rating RISE for each player, which seems perverse?
Players are rated using the following formula:
New Rating = Old Rating + K * (Score - Win Expectancy)
K is a constant (32 for 0-2099, 24 for 2100-2399, 16 for 2400 and above)
Score is 1 for a win, 0.5 for a draw and 0 for a loss.
The Win Expectancy is calculated using the following formula :
Win Expectancy = 1 / (10^((OpponentRating ...[text shortened]... hen calculating your rating.
http://www.playtheimmortalgame.com/help/index.php?help=faq
Originally posted by PolicestateNo, if the two players' ratings are the same, and they draw, then the score is 0.5 and the win expectancy is also 0.5. So the K-factor would be multiplied by zero, and the new rating would be the same as the old rating.
Somebody put me out of my misery. I am not a complete mathetmatical idiot, but this equation seems to predict a small rating RISE for each player, which seems perverse?
Edit - Dang, mcreynolds beat me to it, lol.
Originally posted by mcreynoldsAh. My bold assertion that I am not a mathematical idiot is flawed.
No it doesnt if the ratings are the same then the win expectancy is
1/(10^0+1) = 1/2, and the new rating will be new = old +k*(1/2-1/2) =old
Of course I might have guessed it when I got a win expectancy that predicted 2 wins each, for each time they played!! 🙂 🙂