For as long as I’ve been following sports — at least following it closely as an adult — there has been big tension between what people say about players in hot streaks and what the data shows. Athletes and most people who cover them have accepted hot streaks — whether they be by shooters in basketball or hitters in baseball — as something that actually influence or predict future events. The stats, however — most notably studies of basketball players in the 1980s which led to the recognition of “the hot hand fallacy” — has strongly suggested that recent past performance in small sample sizes do not predict future events.
One new study, however, presents evidence that hot streaks have predictive power. From James Wagner at the Washington Post:
Green and Zwiebel studied two million MLB at-bats from 2000 to 2011. They neutralized for the abilities of the hitter and pitchers — such as lefty-on-lefty matchups and stadium sizes — and focused on 10 major statistical categories, such as batting averages, home run percentages and strikeout rates.
They found that a hitter’s past 25 at-bats were a significant predictor of his next at-bat. When a player is hot, they found his expected on-base percentage to be 25 to 30 points higher than it would if he were cold. Home run rates jumped 30 percent and strikeout rates dropped. For pitchers in hot streaks, future performance was improved, too.
They don’t reach any hard and fast conclusions here, though there are some which seem plausible. Mostly related, I believe, to a new understanding of what is and what is not “random,” as the hot hand fallacy is based on data related to random events. I’m certainly no statistician so I can’t judge either this or other studies in this vein on their merits with any degree of authority. Maybe this supersedes the last best statistical evidence on the matter. Maybe it’s flawed. I have no idea.
My personal takeaway, though, is that there is always something to learn about baseball. And that rather than try to understand it through opinions held based on personal beliefs, authority and predispositions, it’s better to understand it based on the data. Those who skew old school have always been a bit loathe to do this. Now, however, a favorite concept of the statistically-oriented is being questioned. I’ll be curious to see (a) if this new study holds up to scrutiny; and (b) if it does, how the stats folks take to having some long-held beliefs of their own challenged.