Note: this is an FSAS summary of a more in-depth study. For the whole analysis, see the attached document below.
Home-field advantage is one of the most recognized advantages in all of sports. Teams work hard throughout the season to secure the chance to play in front of their home crowd during the playoffs, believing it gives them an edge over their opponents. But how much of an advantage does playing at home actually provide, and how does it compare between different teams? This study explores these questions by analyzing the New York Yankees’ home-field advantage over several decades.
Yankees Home-Field Advantage
To begin, we examined Yankees win-loss records from 1970 to 2023. After downloading the data from baseballreference.com, we examined whether the difference between the Yankees home and away records was large enough to be unlikely a result of chance.
On average, the Yankees won 47.9 home games every year, over 7 games higher than their road average of 40.8 wins. Performing a Z-test (a type of statistical test) on the data confirmed that there was a statistically significant difference between the Yankees road and home performances, with the Yankees enjoying a sizable home-field advantage.
The data in the table below indicates the Yankees’ home and away winning percentages from 1970 to 2023. On a purely visual skim, it appears that this table indicates the Yankees win more often at home than away from most of these teams.
However, we need to confirm this hypothesis through a more robust analysis. The conducted statistical tests are available in the document below, but the conclusion we came to is that there is evidence that the median difference between the home and away records is greater than 0. Therefore, the addition of a home field increased the median winning % for the Yankees over this time frame, and thus we have convincing evidence that the Yankees’ winning percentage at home from 1970-2023 is higher than that of their away winning percentage during that same time frame.
Yankees Home Field Advantage Compared to the MLB Average
In another direction of analysis, we shift our focus to compare the effect of home-field
advantage on the Yankees against the average home-field advantage across the MLB. First, we extract data that reflects the average home-field advantage. With a special interest in the possibly changing trends in home wins over time, this analysis extends the time range of our data collection to the time frame 1901-2023, using data from the Washington Post.
This dataset demonstrates the home win ratio, separated into eight eras of baseball significance. In order to compare this data with the performance specific to the Yankees, we first generate similar era-separated statistics for the Yankees by taking averages of their home win ratios across these time frames.
Additionally, an issue arises in the use of the home win ratio as the statistic of choice;
namely, this variable is dependent on the quality of team (for instance, a better team
would likely have a home win ratio above 1/2 due to their playing abilities and unrelated
to a detectable home-win advantage). In order to eliminate this dependence, we instead
consider the proportion between a team’s home win/loss ratio and their away win/loss
ratio. This is achieved directly in our calculations for the Yankees, and in the case of the
average values, we note that the away winning ratio is equal to (1 − p) for each home-win
ratio p (meaning they will always add up to 1). Thus, these average home/away win proportions are calculated as p/(1−p).
We may test the more interesting question of whether the home/away win proportions feature different means between the Yankees and average MLB scores (this test will effectively tell us whether there is a significant difference between the home-field advantage experienced by the Yankees and that felt overall by the baseball league).
When comparing the averages, there is convincing evidence that the mean is lower for the Yankees than for the average of the MLB teams, meaning that the Yankees actually perform worse at home relative to other teams. Some potential reasons for this could be the Yankees consistently fielding more talented players than the average MLB team, so having home field advantage is less of a boost to them than to a worse team.
We also tested to see if the trajectory of the Yankees home field advantage over the decades is different from the MLB average. When comparing the slopes of the lines pictured above, there was not determined to be a significant difference between the Yankees’ and the MLB average home field trajectories.
Further Research
To further enhance our comprehension of home field advantage, further studies may em-
ploy an analysis that integrates psychological, temporal, and geographical factors. In terms of psychological variables, we could examine media content or interview athletes in order to understand their perspective about home field advantage. Through examining the interactions that occur between the mental states of athletes and environmental signals, we can get insight into the psychological processes that underlie home field advantage. Another line of inquiry is provided by temporal trends, which allow us to compare the home field advantage measures of various historical periods. This temporal lens not only reveals how home field advantage has changed over time, but it also clarifies the contextual factors that have shaped its appearance in different sporting environments. Spatial analysis also offers a chance to examine the concrete spatial factors that affect home field advantage results, like stadium features and travel times. By carefully analyzing these spatial dimensions, we can identify the relationships between competitive dynamics and physical environments.
Full Project:
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