Sunday, February 9, 2014

Maybe the hot hand in sports really does exist

In the early 1980s, Tom Gilovich, then a graduate student at Stanford University, began to wonder which effect we were seeing in basketball when a player suddenly began scoring a lot of points: true hot hand or just random streakiness. ...

But the results showed that their previous shots had no effect on future shots—not even in free throws, with no defender in the way, or in a controlled shooting experiment involving 26 college basketball players. The stat line from future Hall of Famer Julius Erving, a member of that 76ers team that Gilovich studied, seemed to say it all. After missing three shots, he shot 52 percent from the floor on his next shot. And after making three, he shot 48 percent on his next attempt—four percentage points lower. ...

The two new studies, however, are poking holes in the long accepted findings. First, there is one conducted by two finance professors, focusing on baseball. The authors—Brett Green, at the Haas School of Business at the University of California Berkeley, and Jeffrey Zwiebel, at the Stanford University Graduate School of Business—analyzed a mountain of data for their study: 12 major league baseball seasons, or roughly 2 million at-bats. They controlled for variables, like the abilities of the batter and the pitcher, the stadium in which the at-bats took place, and even matchups like lefty versus lefty. And their findings, laid out in a working paper, show that a baseball player on a hot streak is batting 15 to 20 points higher than a teammate who is cold. Home run rates also went up while strikeouts fell—and pitchers enjoyed similar advantages on the mound. ...

[John] Ezekowitz and his coauthors, on the other hand, can say exactly why they’ve been able to identify a hot hand effect in their new basketball study: modern technology. They analyzed 83,000 shots from the 2012-13 NBA season, with the help of cameras that NBA teams had installed at 15 arenas to, according to the study, “provide precise three-dimensional image tracking of the players, referees, and ball every 1/25th of a second.”

With the Harvard graduates able to know the position of the players on the court, they could see that players with recent success in shooting were more likely to be taking shots from further away, facing tighter defenses, and throwing up more difficult shots. “They were more likely to just jack it up,” Ezekowitz said. “Shoot more often.”

So the researchers controlled for these variables—and found what players and fans have long believed: The hot hand does exist. At least a little. According to the new research, players enjoying the hot hand are 1.2 to 2.4 percentage points more likely to make the next shot. Not exactly en fuego, but still.
--Keith O'Brien, Boston Globe, on on fire