A couple weeks ago, I introduced the statistic advanced defensive efficiency. This statistic measures how well a team's defense performs based on the different types of batted balls they face. One of the problems that I had is that I didn't have exact batted ball numbers. Thanks to the Baseball Prospectus custom stat reports, now I do. I also tweaked my formula a little. Before I considered all home runs to be fly balls, now 88 percent of home runs are marked as fly balls and 12 percent are marked as line drives (don't worry, this isn't an arbitrary number). Here's how the new numbers work out:
Old rank- The team's rank in defensive efficiency.
eDER- Expected Defensive Efficiency.
aDER - Advanced Defensive Efficiency.
If any of these terms are confusing, see my previous article on this subject.
These results, which turned out very differently from my original results, shows the big problem with batted ball data: it's very subjective. Baseball Prospectus' interpretation of a line drive is apparently very different from the Hardball Times. Because of this, the final advanced numbers are largely negative. To better capture this data, I would need to recalculate the out percentages using Baseball Prospectus' data, which is impossible.
Nevertheless, I think the rankings are largely correct, just the final number to represent the rank is off. From here, I want to introduce park factors into the equation, something that won't be done until I finish my stat database.