Saturday, July 29, 2006

I typically don't write much about tennis. However, I've just been watching taped coverage on cable television's Tennis Channel of the Dominik Hrbaty-Robby Ginepri quarter-final match in the Countrywide Classic from UCLA's L.A. Tennis Center (UCLA being my undergraduate college alma mater).

I came across the match midway through, and when I heard the announcers saying that Hrbaty had won several straight points, my ears naturally perked up. Being the streak fanatic that I am, I kept rooting for Hrbaty to win more points (or conversely for Ginepri to lose more points) and it kept happening. By the time Hrbaty's run ended, he had won 18 straight points!

This summary on the men's ATP tour website says that Hrbaty won 19 straight points. But even by its own enumeration of the sequence, the article confirms it was actually 18 points:

After a tight start to the match Domink Hrbaty blew open his quarterfinal with Robby Ginepri, winning 19 straight points at one stage en route to a 7-6(0), 6-2 win.

Hrbaty won 19 straight points starting with the last point of the 12th game of the opening set. He then won the tie-break to love, held serve to love to open the second set, then broke Ginepri to love in the second game. He won the first two points of the third game before conceding the first point to Ginepri with a double fault. Ginepri won just 19 second set points.

Last point of the 12th game of 1st set = 1
Tie-breaker 7-0 = 7 (8 cumulatively)
2nd set, 1st game at love = 4 (12 cumulatively)
...........2nd game at love = 4 (16 cumulatively)
...........3rd game, first 2 points = 2 (18 cumulatively)

Inquiry into streakiness -- and other statistical phenomena -- in tennis is not limited to anecdotes, however.

Economist Franc Klaassen of the Universiteit van Amsterdam, in collaboration with Jan Magnus, has published a number of articles on tennis (click here for a list of Klaasen's publications, containing links to the articles themselves). Of particular interest to aficionados of streakiness is the following article:

Klaassen, F.J.G.M. and J.R. Magnus (2001), “Are Points in Tennis Independent and Identically Distributed? Evidence from a Dynamic Binary Panel Data Model,” Journal of the American Statistical Association, 96, 500-509.

By "independent," researchers mean that the outcome of one point has no bearing on the outcome of the next, just like coin-flipping. The opposite would be "dependence," as in streakiness or momentum, where winning one point would increase one's probability of winning the next point.

The aforementioned article studied singles play at Wimbledon. Putting aside the intense statistical aspects, Klaasen and Magnus reached the following conclusion:

The independence hypothesis... is rejected with a p-value of 1.7% (men) and 0.3%(women)... Winning the previous point has a positive effect on winning the current point, both for men and for women,...

(Readers with statistical training will know that for a result to attain "statistical significance," it must have a probability of 5% or less [p < .05] of occurring purely by chance.)

Tennis, in fact, is one of the few sports in which streakiness (or momentum) appears to be fairly well documented, in not just the Klaasen and Magnus study, but also in earlier research by Jackson and Mosurski. Studies of tasks such as basketball shooting and baseball hitting generally have not been able to reject independence (in the various links sections on the right-hand side of this page, see the pages of S.C. Albright, Tom Gilovich, and Jay Koehler, as well as the link to a hot hand bibliography further down, for details).

No comments: