Tennis study shows umpire errors

London: A new study shows irate tennis players are probably right to protest line decisions because umpires are often wrong when challenged on whether a ball is in or out.

A University of Sussex analysis of players' challenges in 15 professional tennis tournaments in 2006 and 2007 found line judges were wrong 40 per cent of the time.

Researchers compared the official records of nearly 1,500 challenges by almost 250 players using a laser system called Hawk-Eye that records exactly where the ball strikes the ground in 3-D.