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Probability of Hitting a Home Run

Jan 6, 2011 | By Beverly Bird
Probability of Hitting a Home Run
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According to the Book of Odds, a major league baseball player has a 1 in 35.26 chance of hitting a home run each time he goes up to bat. But before you start mathematically calculating which of the next at bats will produce a homer, consider this: the 1 in 35.26 home run may have occurred in a scientific vacuum. The weather, your mood, the pitcher and the ballpark you are playing in all affect the likelihood that the ball you hit will sail out of the park. Since the 1990s, the use of steroids among professional baseball players has also skewed statistics, making home runs seem more likely than they actually are for the average player.

Real Statistics

Before steroids, in an era when indoor stadiums that were immune to the weather were still a thing of the future, Roger Maris broke Babe Ruth's home run record in 1961. The Houston Astrodome, the first domed stadium, would not open its doors until 1965. Maris had 61 home runs in 698 at bats. So including variables such as wind and heat to help the ball along, Maris hit one home run for every 11.44 times he was up to bat that season. Likewise, Hank Aaron hit a homer one in every 16.37 at bats, Willie Mays did it one in every 16.48 at bats, Mickey Mantle one in every 15.11 at bats, and Ted Williams one in every 14.79.

Effect of Steroids

The use of steroids by Major League players had a major impact on the sport's statistics. According to Robert Adair in "The Physics of Baseball," the bigger you are, the more bat speed you will generate when swinging. For instance, when he weighed 206 lbs., Barry Bonds swung the bat at 67.34 miles per hour. When he weighed 228 lbs. after steroid use, he swung the bat at 68.81 mph. According to ESPN, bat speed affects home run probability. Alan Nathan, a physics professor at the University of Illinois, says that each mile per hour of bat swing equals approximately 6 additional feet of distance. The faster you swing the bat, the harder you will connect with the ball and the farther it will go. Steroid use increases weight and the odds of hitting a home run.

Effect of Ballpark

Not all ballparks are created equal. Some give up more home runs than others because the distance to the fence -- which the ball must go over to be a home run -- is shorter. For instance, U.S. Cellular Field in Chicago allowed an average of 2.76 home runs per game in 2008. AT&T Park, where the San Francisco Giants play, averaged only 1.48 home runs a game that same year.

Intangibles

Finally, some components cannot be defined. Athletes go on winning and losing streaks that may have nothing to do with the weather, the ballpark, or how much they weigh. When things are going well for them, they're self-confident and may swing harder and hit better. When things are going well for the pitcher, he becomes self-confident and may throw better. In the final analysis, the probability of hitting a home run during the at bat in the major leagues depends on where you are, how you feel, how much you weigh and whether it is hot enough for the air to help the ball out of the park.

References

Article reviewed by Allen Cone Last updated on: Jan 6, 2011

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