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Overview. Forecasting: one aspect of a larger tennis projectMotivation for forecastingHow to compute forecasts during a match?Forecasting in practice: graph of the 2003 Ladies' Singles Wimbledon finalRobustness of the graphConclusion.. Tennis project. Testing hypotheses (six papers):7th game
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1. Forecasting the Winnerof a Tennis Match Franc Klaassen
University of Amsterdam (NL)
Jan R. Magnus
Tilburg University (NL)
TST Congress, London
July 29, 2003
2. Overview
Forecasting: one aspect of a larger tennis project
Motivation for forecasting
How to compute forecasts during a match?
Forecasting in practice: graph of the 2003 Ladies’ Singles Wimbledon final
Robustness of the graph
Conclusion.
3. Tennis project Testing hypotheses (six papers):
7th game is the most important game in a set: false
Real champions win the big points: true.
Service strategy (in progress):
How to choose the strengths of 1st and 2nd services to maximize the probability of winning a point?
Rule changes (one paper):
How to reduce the service dominance? Presented at TST-1.
Forecasting (two papers):
Forecasting winner while match is in progress: TST-2.
4. Motivation for forecasting Forecasting the winner of a tennis match:
Before a match
Using odds from bookmakers
Using statistical model, e.g.,
Boulier and Stekler (1999)
Clarke and Dyte (2000)
During a match
Using statistical model
? focus of our paper.
5. Why forecasting during match?
TV spectators want information on:
Which player leads at this moment?
Who is most likely to win the match?
How did the match develop up to now (momentum, winning mood)?
6. TV spectators get info on Score: gives info on
1 (Leader): Yes
2 (Likely winner): Partially
4-6 for Agassi-Hewitt => Hewitt will probably win,
4-6 for Agassi-Henman => Agassi will still be the favorite
3 (Development up to now): Partially
5-5 can result after 4-4 (match in balance),
but also after 5-0 (one player is in a winning mood)
? Room for improvement regarding 2 and 3.
7. TV spectators also get info on Match/set stats (%1st serve in,...): give info on
2 (Likely winner): Not much
3 (Development up to now): Partially
Comparison of 2nd set with 1st set statistics gives some insight,
but each statistic is too aggregate to give a clear picture.
Note: summary stats provide detailed info on specific aspects of each player ? useful, but beyond scope of our paper.
? Still room for improvement regarding 2 and 3
? Purpose of current paper.
8. Idea Present the probability that a player will win match; update it as match unfolds (real-time forecasting).
Example: Agassi-Hewitt
At start of match: Agassi wins with prob. 60%
At 4-6: Agassi wins with prob. 30%
At 4-6/0-3: Agassi wins with prob. 20%.
Use graph to visualize the probs. of all points till now.
9. How to compute the forecasts during a match? Suppose: match between players A and B.
Goal: Prob{A wins match} at each point up to now.
This probability depends on 2 inputs (besides score):
Prob{A wins match} at start of match
Prob{A wins point on serve}+Prob{B wins point on serve}.
Implementation using our computer program TENNISPROB:
Choose the two inputs before the match and keep them constant
Type in the score at each point
? TENNISPROB gives Prob{A wins match} very quickly.
10. How to choose the two inputs?
Prob{A wins match} at start of match
We provide an estimate based on rankings (e.g., 80%),
but one can easily improve/overrule that estimate if one has specific other info (injury problems, specific ability of surface,...) (e.g., 70%)
? In the end there is one starting point of the graph (70%).
Prob{A wins point on serve}+Prob{B wins point on serve}
We provide an estimate based on rankings (e.g., 120%: both players win 60% of their points on service)
No need for adjustment: the graph hardly depends on our choice
? There is an estimate (120%).