Examining the curious home run totals of the New Yankee Stadium

The New Yankee Stadium appears to be a hitter's paradise through its first six games. There have been 26 home runs hit in the first two series, for a staggering 4.33 home runs per game. For comparison purposes, the first year of Coors Field saw 3.34 home runs per game, the last year in Yankee Stadium saw 1.975 home runs per game, and there were 2.00 home runs per game in the American League last year. Here, we will examine if the number of home runs in the New Yankee Stadium is statistically significant compared to the number of home runs in the old Stadium and in the American League in general, as this difference could be due to chance alone.

First, we will examine whether or not there are more home runs in the New Yankee Stadium gives rise to more home runs than the old stadium. To do this, we will perform a one-sided t-hypothesis test. Basically, a hypothesis test is when you test if something (a null hypothesis) is true. Our null hypothesis is that the New Yankee Stadium is no different than the old one, i.e., the true mean value of home runs per game is 1.975 as it was in the old stadium. The alternative hypothesis is that the true mean amount of home runs in the New Yankee Stadium is greater than 1.975. For us to reject the null hypothesis in favor of the alternative, we will have to perform a test. If this test gives us enough evidence, we will reject the null hypothesis, otherwise we will accept the null hypothesis. The test statistic is called t. If t is greater than a certain value determined by the level of the test and the degrees of freedom, then we will reject the null hypothesis. The level used for this test will be .05 and the degrees of freedom is 5 (n - 1, n = 6, 6 - 1 = 5). The test statistic for this particular test is 2.015 (Level of .05 means the following: If the true mean home runs per game is 1.975, we would obtain a t > 2.015 only 5% of the time). So, if our t-statistic is greater than 2.015, we will reject the null hypothesis. Based on our data, we obtain a t = 2.397. Because this is greater than our test statistic 2.015, we reject the null hypothesis that the true mean home runs per game is equal to that of the Old Yankee Stadium and conclude that the true mean home runs per game is greater than that of the Old Yankee Stadium.

Next, we can see if there are a statistically significant amount more home runs in the New Yankee Stadium compared to the entire American League, using data from last year. There were 2.00 home runs per game in the American League last year. Our null hypothesis is that the true mean number of home runs in the New Yankee Stadium is 2.00, and the alternative is that the true mean number of home runs in the New Yankee Stadium is greater than 2.00. Bypassing the explanation of the calculations as they were the same as the last one, we obtain a test statistic of 2.015. As before, if we obtain a t greater than 2.015, we will reject the null hypothesis, otherwise we will fail to reject the null hypothesis. We obtain a t = 2.278. Once again, we have enough evidence to reject the null hypothesis and conclude that the true mean number of home runs per game in the New Yankee Stadium is greater than the 2.00, which is the mean number of home runs per game in the American League.

Conclusion
Interestingly enough, we have found that the high number of home runs in the New Yankee Stadium is statistically significant. It remains to be seen if this stadium will be the new Coors Field, but even that is certainly a possibility. The ramifications of this apparent miscalculation could be severe for the Yankees. They are a franchise that has predicated itself on being able to buy whoever they want, hitting and pitching-wise. While this should not affect their hitting, it will damage their ability to buy pitching. Signings like A.J. Burnett and CC Sabathia may not have been possible. To continue getting solid pitching, New York will have to pay more, which in the past has been no problem, but if the economy does not recover in the near future and if the Yankees do not sell out their stadium, there may be issues down the road because of this stadium.

Interesting Baseball Fact of the Day: The record for most home runs in a game is 12. This was set by the Tigers and White Sox twice, on May 28, 1995 and July 2, 2002.