How can tennis star Roger Federer have won only 54% of the points he played, but been the best player in the world? Jeff Sackmann, the tennis stats brain behind tennisabstract.com, explains to Tim Harford how probability works in the sport.

Presenter: Tim HarfordProducer: Debbie RichfordSeries producer: Tom CollsProduction co-ordinator: Brenda BrownSound Mix: Nigel AppletonEditor: Richard Vadon