Division 3: Westbury David Lloyd Women's winter B v Chippenham Olympiad A (Thu 26 Feb 2009)

Match played between Sarah Thomas (home) and Lara Sherwood (away).
Match won by Lara Sherwood. Result: 6-9,5-9,9-5,6-9:9-1,9-2,9-1:10-8,9-5,7-9,9-10,5-9:1-9,5-9,9-5,9-4,0-9:9-1,9-1,9-6.

Starting level for Sarah Thomas: 652, level confidence: 54%.
Starting level for Lara Sherwood: 491, level confidence: 73%. Set manually.
Sarah Thomas to win as she is currently playing 33% better than Lara Sherwood.

Lara Sherwood won 75% of the games and 55% of the points.
This games result would be expected if she was better by around 25%.
This points result would be expected if she was better by around 11% (english scoring).
These are weighted and combined to calculate that Lara Sherwood played 20% better than Sarah Thomas in this match. An upset!

Assuming that any level changes are shared between both players, for this result it looks like Lara Sherwood actually played at a level of 621 and Sarah Thomas at a level of 516. Without any damping, both players would need to be adjusted by 26% to match this result.

Allowing for the difference in level between the players, the adjustments have been reduced to 23% and 23% respectively.

Factoring in the relative levels of confidence which allows players with low confidence in their levels to change more quickly, the adjustment for Lara Sherwood changes to +17% and Sarah Thomas changes to -23%.

After applying standard match damping, the adjustment for Lara Sherwood becomes +9.6% and for Sarah Thomas becomes -12%.

Apply match/event weighting of 75% for 'Womens Spring 2008/2009' so the adjustment for Lara Sherwood is +7.2% and for Sarah Thomas is -9%.

Apply limits to the amount of change for a single match which are based on player level, level confidence and time since last match so that Sarah Thomas is limited to -5% level change. In general a player's level won't go up by more than 10% or drop more than 5% if they've played in the last 7 days but those limits are relaxed if their previous match was further back.

Increase level confidence due to one more match played. Lara Sherwood: 86%, Sarah Thomas: 74%. Reduce level confidence based on how unexpected the result is. Lara Sherwood: 68%, Sarah Thomas: 58%.

A final adjustment of -0.1% has been made to both players as part of the automatic calibration that is performed after each match. All players in this pool will have been adjusted equally in order to remain equivalent to other player pools.

Final level for Sarah Thomas: 620, level confidence: 58%.
Final level for Lara Sherwood: 526, level confidence: 68%.

Notes

• This calculation is done in two main parts; first work out the adjustment needed to match the results and then apply damping. This means that levels should always be 'about right' but the time taken to get there or the volatility is dependent on the damping.
• A level also has 'level confidence' which drops if players haven't played for a long time or have had enexpected results. As low confidence levels adjust more quickly than high confidence levels, it allows these players to find their level more quickly without impacting their opponent's level too much.
• Point scores are used as well as game scores for accuracy - particularly important for 3-0 results - though we can work with game scores only too, albeit with more damping.
• Mismatched players are allowed for - you don't have to hammer your opponent. See explanation above if this applies to this match.
• The section on damping is where we still have some options. We have recently made a change to damp league matches more than tournament matches and box matches even more than that. This gives added weight to the more important matches.
• There are occasional, very small adjustments made to all players to keep the averages constant which are not covered here.
• You don't get a bonus just for winning - if you want to go up you have to play better than expected against your opponent.
• We have spent more than 5 years fine tuning the level calculations based on tens of thousands of match results and a great deal of feedback from players, team captains and coaches. It's the most usable and accurate ranking system there is in any sport, let alone squash.
• For a more complete explanation of how levels are calculated (on which this system is based) see the help file here.
• If you have thoughts/opinions on the above or any feedback on the way levels are calculated or updated, please contact us. We welcome all feedback, although we are keen squash players ourselves and would pefer to be on-court than in front of a screen so please be patient and please do try to see if your question has already been answered on the help page. We are unable to answer questions about hard anyone played in their match - we only get to see the results - and if your level didn't increase as expected please make sure you've looked at the above explanation before contacting us. If you want to go up the levels, train harder, listen to your coach and win more points. Or just be incredibly talented!