Today we looked at the lengths of baseball games. Most games like football, basketball and soccer have periods or quarters of a set length. Baseball is different -- it ends after 9 innings (or 8 1/2 innings if the home team is leading in the ninth).
What did we learn?
1. Baseball games in 2007 averaged 175.5 minutes -- almost three hours. In contrast, the median length of baseball games in 1967 (40 years ago) was 150 minutes -- about 25 minutes shorter than 2007 games. I'm not sure why this is true. Is it due to the greater number of pitchers? Or perhaps due to the TV commercials?
2. To understand the reasoning for the variation in the lengths of baseball games, we looked at the relationship between TIME.OF.GAME and several predictors including number of AB, number of Hits, number of SO, and BFP (batters faced pitcher). The strongest association was between BFP and TIME.OF.GAME. In contrast, there was little association between SO and TIME.OF.GAME.
3. We can measure both the direction and strength of association with a correlation r. I described several properties of r and we got some practice matching up values of r and the corresponding scatterplots.
4. I concluded with some fundamental ideas from sabermetrics (the scientific study of baseball data). What is the best batting measure among AVG, OBP, SLG? Can we find the batting measure that is better than AVG, OBP, SLG? We'll address these questions next class.