When you play in competitive Scrabble, you'll know more about ratings and maybe get your own. Rating is a measurement of the performance of a player. If a player has a high rating, he/she is probably a good player. Usually a player who plays in national-scaled tournaments will get national rating and a player who plays in international tournaments will get his/her own international rating from WESPA. Of course the tournaments must be rated to get the ratings. National rating and international rating of one player are not exactly the same.
Some tournaments apply division or section system. This system is divided by ratings. Players with higher rating play in higher division, while players with lower or no rating play in lower/open division. This brings extra competitiveness into the tournaments.
Player's rating under 50 rated games is still considered as provisional rating means that his/her rating is still unstable and not valid enough. WESPA's new rating formula decreases the minimum games to 30 games. After a player passes the minimum games mark, his/her rating will be stabler and truly depict his/her performance. Some players may be overrated or underrated, this could happen in tournaments depends on the opponents they face, also the number of rated players in tournaments.
If a player who has higher rating playing in a tournament which is joined mostly by players with average rating, he/she could probably lose some of his/her rating points if he/she don't play well. Even a player could lose his/her rating although this player finishes top.This also applies to players who have lower rating. Low-rated player could easily get rating points from players with higher rating, should this low-rated player win against players with higher rating.
Here is a link from Scrabble Australia on how rating changes :
http://scrabble.org.au/ratings/system.htm
Example : You are rated 1453. You win 5 out of 7 games against opponents whose average rating is 1393.
1. You are 60 points higher on average.
2. Your probability of winning a game is on average = 50 + 1/12 of 60 = 55%
3. You would be expected to win 55% of the 7 games, ie 3.85 games.
4. You actually won 5 games, which is +1.15 games better than expected.
5. A multiplier of 20 usually applies. Your rating gain is 1.15 x 20 = 23 points.
To wrap things up, rating isn't everything but only as a measurement. It's also not completely valid if you only play one or two tournaments. Losing some isn't the end of the world and gaining some isn't the end of the road :)
ISF Ratings : http://indonesianscrabble.org/ratings/ranking
WESPA Ratings : http://www.wespa.org/aardvark/cgi-bin/rating.cgi
Additional info:
ReplyDeleteFor those playing chess, the rating used in ISF and other is a modification of ELO rating, unlike chess we can calculate how much exactly the spread in game, so in other to make a fairer rating calculation, scrabble slightly modified the ELO rating and it has formula like this:
R1+ K * [W- 1/(1+10^(R2-R1/400))
K = 20 + (D/10)
R1= Your rating
R2= Your opponent rating
W = 1 if win, 0,5 if tied, 0 if lost
D = Margin (Maximal value = 200)
This is rating calculator
http://www.3dkingdoms.com/chess/elo.html
K: (20+(margin/10). Maximal value for margin is 200
About the calculation in australian website, if accurate enough and simplify much. But the only accurate calculation can for 1 game ONLY can be found there... The accurate calculation is very hard to count, and since we have prat cooker that can calculate it by simple click, just wait until ISF admin post in web...
The accurate calculation is very hard to count due to this:
First, the formula above only applied if BOTH player has already played 50 or more games. The formula below 50 games used in prat cooker is still mystery. However, it proved fair enough.
Second, after every game in tourney, your and your opponent rating will be slightly different than rating stated in ISF website, since prat cooker count rating change round by round, not tourney per tourney. Every game finished in that tourney, you and your opponent will get some additional and penalty rating.
About winning probability, of course scrabble has a different winning probability, even though it basically use same tool to calculate rating. Luck factor in the scrabble is much higher than chess. In chess, it almost unlikely that player rated 500 below can win, but record show that even the player rated 500 points below (and both player are not overrated and underrated), that player has a winning chance about 10-15%. Even if you rated 1000 points below, you still have a very little chance to win the game. The combination of good tile for lower rated player and bad tile for higher rated player sometimes enough to make the much lower rated player to get a narrow win. So don't be afraid to play against high rated opponent, because in scrabble, no opponent are impossible to beat