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Statisticians play “Moneyball” to accurately predict how weather impacts baseball


block_n-2646902-5476491As Major League Baseball heads into the post season, a study completed at the University of Nevada, Reno offers insight into how weather and, more specifically, temperature may impact teams’ performance. The published research project, “The Impact of Temperature on Major League Baseball,” applies statistical data analysis to determine how temperature plays a role in the MLB.

The study evaluated 22,215 games, spanning the 2000-2011 regular seasons. Temperature was categorized as “cold,” “average” and “warm.” Analyses were performed on all MLB games, games played in the National League, games played in the American League and games played in 23 different stadiums currently being used by MLB teams. Home and away teams’ performances were analyzed separately for each population of games.
Brandon Lee Koch, who conducted the research as a McNair Scholar at the University of Nevada, Reno, worked alongside University mathematics and statistics professor Anna Panorska to complete the study.
The two found that commonly referred to MLB statistics – runs scored, batting average, slugging percentage, on-base percentage, and home runs – significantly increase, while walks significantly decrease, in warm weather compared to cold weather. The study also revealed that the American League shows a stronger association between temperature and many of the offensive statistics than the National League. It suggests this may be a result of the offense being impacted by temperature more than pitching and defense as a result of the varied rules between the leagues –American League teams use a designated hitter to bat for the pitcher and National League teams require their pitchers to bat.
In addition to analyzing how temperature impacts MLB statistics, the study also examined individual stadiums. It offers insight into which stadiums are affected by temperatures the most and the least. According to the study, an increase in runs scored from cold to warm is seen in 18 out of 23 stadiums (78.2 percent) for both the home team and away team. The San Francisco Giants, Oakland Athletics, Baltimore Orioles, New York Yankees and Philadelphia Phillies showed the most significant increase in runs scored from cold to warm at their home stadiums. Conversely, significant stadium increases in runs scored by the away teams (or runs allowed by the home teams) were seen at the Kansas City Royals Kauffman Stadium, Chicago Cubs’ Wrigley Field, and Baltimore’s Orioles Park at Camden Yards.
So what does all of this mean for the MLB going into the post season?
“It could be beneficial for managers of MLB teams to take game day temperature into account when setting their lineups,” Koch said. “For instance, if a manager is having difficulty choosing between two players for his starting lineup, and one player is a more patient hitter and tends to draw more walks than the other player, the manager might benefit from starting the patient hitter in cold temperatures.”
The use of statistical data analysis isn’t uncommon in baseball. As seen in the 2011 film Moneyball, Oakland A’s General Manager Billy Beane used statistical data to analyze and place value on players he picked for the team.
“As an educator, it’s important for me to get across what you can do with mathematics and statistics,” Panorska said. “It’s an incredibly versatile field with many applications in diverse fields. People often tell me that it’s too abstract. It’s because it’s so abstract that it is so useful. As a profession, statistics offers a lot of opportunities, including working in interdisciplinary teams and the ability to help people working in any number of fields – including baseball.”
Koch first approached Panorska about the study he wanted to complete as part of his McNair Scholars Program undergraduate research work. They worked together on the study for six months, ultimately getting published in Weather, Climate and Society, a journal of the American Meteorological Society  in October 2013. Koch graduated from the University of Nevada, Reno in May 2013 with a bachelor’s degree in mathematics and received direct entry into the biostatistics doctoral program at the University of Minnesota on full research scholarship.
“Brandon is an incredibly talented and hard-working student,” Panorska said. “It was his idea to do this study and in all my years as a professor and statistician, I’ve never had a published paper receive so much recognition.”
Research funding for the study was partially provided through the Ronald E. McNair Post-Baccalaureate Achievement Program. The complete copy is available for download through the American Meteorological Society and can be found here. The study is also available in the University’s newsroom.
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