Tuesday, April 1, 2008

Opening Day (Part 1): Roger Clemens is Innocent

I’m excited to join such a distinguished group of bloggers, and proud to reveal a new analytic insight in my first post.

It seems to be the consensus among baseball fans that Roger Clemens used performance enhancing drugs in the latter stages of his Hall of Fame career. Accusers support their claims by referring to his apparent improvement when he left the Boston Red Sox for the Toronto Blue Jays before the 1997 season, right before his age-34 season. But advanced analytics tell a different story altogether.

Using some new functionality in the latest version of SAS, I created two new metrics. One is something I call Adjusted Prevented Runs (In League). Basically, it controls for a handful of factors not addressed in the pitching metrics most favored by sabermetricians today and in one number tells you how effective a starting pitcher is, relative to the rest of the league, in keeping the opposing team from scoring. I call the second metric Factored Outs Over League, because in terms of pitching performance, while keeping opposition runs down is the ultimate goal, the way to achieve it is by getting outs. It’s like a pitcher’s version of On Base Percentage.

Because of the relationship between preventing runs and getting outs, the best way to get an overall view is to multiply the two metrics. And when you look at the data, Roger Clemens didn’t actually register a significant change in his performance from his Boston years to the Toronto years.

Thus, with the help of APR(IL)*FOOL, the power of analytics is demonstrated once again: this time, to clear the name of an innocent American.

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