Tuesday, July 8, 2008


Today we talked about one big idea and then had our 2nd Fathom lab.

When you hear that some historical player had a .372 batting average, you should ask ...
1. When season did the player get this batting average?
2. Where did the player play ? (The ballpark could have influenced his batting average.)
3. How many at-bats? (We'll see that it is easier to get a high batting average with a small number of at-bats.)

To really understand the greatness of a historical batting average, we look at the player's average in the context of all batting averages of regular players that season. If we compute the mean and the standard deviation of the batting averages, then we compute the z score

z = (AVG - mean)/s

This tells you how many standard deviations the guy's AVG is above or below the mean. If z = 4, that is a wow -- his batting average is four standard deviations above the mean.

In the Fathom lab, we compared the offensive stats of the American League teams and the National League teams this season. We learned that the AL teams tend to score more runs per game. The slugging percentages of the AL teams are pretty similar to the slugging pcts of the NL teams, but the AL teams seem to be better in getting on base. Since the AL teams tend to be better on OBP, they tend to score more runs.

Why is the AL better? There are likely several explanations, but the fact that the AL has the DH probably helps them score more runs.

1 comment:

deborahhendricks said...

I found the following article on Y! Sports tonight and thought it was rather interesting.


How baseball is rigged for lefties
By LiveScience.com Staff
8 hours, 7 minutes ago

Buzz Up PrintIn the general public, about 10 percent of people are left-handed. In Major League Baseball, about 25 percent of players are lefties. Any serious fan knows some of the reasons why certain positions favor lefties, but David Peters has come up with a laundry list of reasons to explain this anomaly.

Peters is an aircraft engineer and professor at Washington University in St. Louis, and a devoted Cardinal’s fan. This week, he shared his reasons why the game is rigged to favor southpaws.

The ballparks: Right field in most parks is shorter than left field because of the preponderance of right-handed hitters.

Seeing the ball: “A right-handed batter facing a right-handed pitcher actually has to pick up the ball visually as it comes from behind his (the batter’s) left shoulder. The left-handed batter facing the right-handed pitcher has the ball coming to him, so he has a much clearer view of pitches.”

Getting going: After a right-hander connects with a ball, his momentum spins him toward the third-base side. He must regroup to take even his first step toward first base. A left-hander’s momentum carries him directly toward first. “The left-handed batter has a 5-foot advantage over the right-handed batter,” Peters calculates. “And that means the lefty travels the 90 feet to first roughly one-sixth of a second faster than the righty. That translates to more base hits for the left-hander, whether singles or extra base hits because lefties are getting to the bases more quickly.”

Pitching: The left-handed pitcher generally is much more difficult to steal off. From his stretch, he peers directly at the runner; the right-hander must look over his shoulder and wheel to first base, giving the runner more of a warning of the pitcher’s intent.

Fielding: First base and right field favor lefies. The favorable angles lefties allow them to throw the ball more quickly across the diamond to second, third and home.

Just being different: “Because only 10 percent of the population is left-handed, kids grow up and mature in baseball seeing a left-hander just 10 percent of the time they bat,” he points out. “So, it can be hard for both lefties and righties to face a southpaw. It’s why some left-handed batters look dreadful matched against a lefty.” Some batters don’t like facing southpaws because their ball is purported to have a natural movement away from a right-hander and into a lefty. “There’s no scientific evidence to support this, but I wonder if lefties get that movement from learning to write in a right-hander’s world,” Peters says.

Not catching on: One position a lefty rarely plays is catcher; it is difficult for a southpaw catcher to throw over so many right-hand batters.