The form rating has been developed to provide an indication of the level of a player’s form over the last 5 tournaments. It is intended to complement the main Snooker Rating, which is designed to reflect the relative underlying ability of each player.
The basic principle of the rating system is that the expected result of a game is dependent on the relative ability of the two competing players. Flipping this around gives a formula for rating the result achieved by a player given the ability of their opponent.
Form rating = Opponent’s snooker rating * frames won / frames lost
For example, if Player A defeats Player B 6-3 and Player B’s snooker rating before the match was 500 then Player A’s form rating is 500 * 6 / 3 = 1,000.
Similarly, if Player A’s snooker rating was also 500 then then Player B’s form rating would be 500 * 3 / 6 = 250.
Note that the calculation of a player’s form rating is independent of their own snooker rating – we make no allowance for whether or not the player was expected to win the match.
Basing a player’s form on a single match, or even a whole tournament, isn’t particularly reliable. Instead I will calculate a form rating based on all matches played in the last 5 tournaments.
If a player didn’t compete in one of these events then their rating is simply based on their performance in the other 4. If a player didn’t compete in any of these events then their rating will be 0.
As with the Snooker Rating system, it is performance in ranking events that will be taken into account (including PTC events). The only additional tournament to be included is The Masters – the most prestigious of the invitational events.
The form ratings are only intended to be a guide, a mathematical interpretation of the results of games. They make no attempt to assess whether these results have arisen because one player has played particularly well, or the other particularly poorly. They make no attempt to take into account any match statistics such as safety success / pot success / highest breaks made.
The ratings also give the same weight to every frame played, regardless of the stage of the tournament or the state of the match. While in theory this should be a sound assumption to make, in reality it does have a significant impact. Some players will have a relatively high form rating based largely on their performances in the qualifying rounds of events, but this doesn’t necessarily mean that they will be able to reach this standard in the final stages.
A more sophisticated measure would attempt to take these factors into account, but that is beyond the scope of this system.
James Collingwood – 3rd March 2013