Statistics and Baseball

This weekend, Barry Bonds hit his 714th home run and he is currently tied with Babe Ruth for the most career home runs. Also Albert Pujols has currently hit 22 home runs in 44 games and is on a pace to hit 81 home runs this season. We again look at home run hitting. Here are the class highlights:

• Last week, we saw that some statistics like OBP and OPS tend to be bell-shaped. In this case, we can predict the proportion of statistics in particular intervals if we know the mean and standard deviation. This is called the 68-95-99.7 rule
• We look at three big home run seasons, 1921 (when Ruth hit 59 home runs), 1961 (when Maris hit 61) and 2001 (when Bonds hit 73). The above graph shows the home run rates of all regular (at least 300 AB) players for those three seasons. By use of standardized scores, we can see that Ruth's 59 home runs was the best accomplishment relative to his peers.
• We watched a segment of the movie 61* that documents Roger Maris' accomplishment of hitting 61 home runs. The wives of Roger and Babe Ruth watched the accomplishment together in the stands -- it doesn't appear that Ruth's wife was very happy about the record being broken.
• This week we start talking about how one compares two or more batches of data. To start, we looked at the batches of home run rates for the 1921, 1961, and 2001 seasons. We can compare the batches graphically by means of parallel boxplots. Also I introduced a rule of thumb to check for outliers. Although this isn't that suprising, we determined that Ruth, Maris and Bonds were outliers with respect to home run rate for those seasons.