RISPA Ratings Calculations
How is your RISPA rating calculated ?
Your RISPA rating is calculated as the average (arithmetic mean) of your
individual
"Game Ratings"
from all your "Contributing Games".
What does this mean ?
Firstly "Contributing Games" are all those RISPA rated games you have played
in
the current
year
or in the two
previous calendar years, including only your
most recent events
up to a maximum of 8 events.
For any game, your "Game Rating" is calculated as follows :
your opponent's rating +50 if you win
your opponent's rating if the game is drawn
your opponent's rating -50 if you lose
subject to the conditions that
i) your game rating for the game is at least your current rating +10 if you win and
ii) your game rating for the game is at most your current rating -10 if you lose
This is usually referred to as the 40-point rule and can be expressed this way :
if you beat someone
whose rating is 40 points
or more less than your own then
your game rating for the game is your rating + 10
Similarly if you lose to someone who is 40 or more points above you then
your game rating for the game is your rating - 10
Example:
Let's keep it simple, imagine you start out and play a 3 game event* ...
Game 1: You play a player rated 150, you lose -
your game rating for this game is 150 - 50 i.e. 100
Game 2:
You play a player rated 100, you win -
your game rating for this game is 100 + 50 i.e. 150
Game 3:
You play a player rated 120, you win -
your game rating for this game is 120 + 50 i.e. 170
After the tournament your RISPA rating is calculated as described above
from your 3
contributing games,
i.e.
as the average of these individual
game ratings.
You can work this out by simply totting up these
game ratings and
dividing by the
number of games you have played, like this :
Tot them up: 100 + 150 + 170 = 420
Now divide by 3 i.e. 420 / 3 = 140
That's it! 140 ! Your rating going into your next event will be 140 !
Is this reasonable?
Well, you scored 2 points out of 3 against players
whose average rating
is (150 + 100 + 120) / 3 i.e. 370/3 i.e. 123.3
So it seems fair enough based on this small sample of three games.
What happens next ?
Well, sporting your laudable 140 rating you play in another tournament ...
and you are drawn against Mr. Scrabble whose rating is 200 and
you lose - tsk !!
Calculated the normal way your game rating for this game
would be
200 less 50 = 150, but this (150) is HIGHER than your current rating
of 140
and you LOST, therefore condition ii) above applies.
It wouldn't make sense for you to benefit from a loss would it ?
Thus your game rating for this game is calculated
as
your own rating less 10
i.e. 140 - 10 = 130
Now, it's the end of tournament - this was a 1-game tournament
or you went home early or your writer got fed up with this example
and it's time
to calculate your NEW rating.
Okay, you have now played 4 games in 2 tournaments.
Your NEW RISPA rating is calculated, again by totting up all your individual game ratings
and dividing by
the number of games you have played, so
(100 + 150 + 170 + 130 ) / 4 i.e. 550 / 4 or 137.5
And that's it! 137.5 is your new RISPA rating.
So you've dropped a little (140 to 137.5) after your loss to the great 200 player.
Never mind ... there'll be another tourney soon enough to add some big figures
into your ratings calculation ... Meantime, you can work out what your rating would
have
been, if only you had won that last encounter (clue : 650 / 4 )...
* note that RISPA rated tournaments to date have only been of 12 or 13 games