More On Roger Clemens

Last week, Justin Wolfers offered an insightful analysis of Roger Clemens‘s career statistics and what those statistics imply about the likelihood that Clemens used steroids.

The latest contribution to this debate is by sabermetric legend Nate Silver of Baseball Prospectus. Using only data through 1997, Nate generates a projection of what Clemens‘s stats should have looked like from 1998-2001, the years in which the Mitchell report alleges that Clemens used performance enhancers. Silver concludes that there is nothing particularly unusual about the pitcher’s performance during this four-year period.

Does this conclusion vindicate Clemens? Not by a long shot. While statistical evidence can sometimes provide convincing evidence that something really out of the ordinary has happened (like the sumo wrestling cheating that was documented in Freakonomics), it is far from clear how to interpret the findings when things look normal. Indeed, most of the studies that have examined data on steroid use in baseball have found little evidence that steroids actually enhance performance. Stephen Stigler, a statistics professor here at the University of Chicago, came to that conclusion. So does Nate Silver in a prior analysis. The only exception I know is Ray Fair‘s study on age effects in baseball, in which he shows that almost all of the batters in his sample who far exceed his predictions late in their careers played during the 1990s.

Data are great, but in this instance analyzing dirty syringes or subjecting old blood samples to new doping tests are both more likely to provide definitive answers.

(Hat tip to Ken Kovash)

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  1. ML Harris says:

    Interesting: The frequently jaundiced eye of economics sees statistics as able to prove cheating but not to disprove it.

    I don’t mean to take the science down a peg, but last week, we were convicting Clemens because one study (flawed due to the statistics used). Today, we are leaving him convicted, despite a reasonable study suggesting otherwise.

    I don’t really care if Clemens used. Or Bonds for that matter. Detestable though they may be, it’s in the way of my enjoyment of the strategy and majesty of the game.

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  2. Kevin L. says:

    If the data revealed shows that steroids aren’t enhancing performance, then what are the players’ incentives for using it? If you showed a player that he was playing about the same before and after using the steroids, then would they still use it?

    Now I know we’re trying to figure out if these players used steroids in the first place. But let’s say we live in a world where steroids were natural and legal. And let’s say that the accused all did use steroids. So what this post is saying is that the substance really did nothing for the players. I’m not refuting Levitt’s claim that lack of change in the data should vindicate the players. I’m asking why isn’t the performance data showing anything. If people can show that steroids don’t help, then we would stripping the perceived effectiveness and need to take performance-enhancing drugs that don’t really enhance.

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  3. Christopher says:

    If steroids doesn’t affect performance, should we care? Does the intent to get ahead illegally without actually benefiting count as cheating?

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  4. scoey says:

    It would be easy if people just told the truth.

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  5. Brian says:

    “Does the intent to get ahead illegally without actually benefiting count as cheating? ”

    -Ask Pete Rose what he thinks…not only didn’t ‘cheat’ persay but also (as far as I’ve read) only bet FOR his team to win. Nonetheless, deemed so unsavory he’s been banished for life.

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  6. Kyle S says:

    Ray Fair’s initial study had a number of problems with it as chronicled by Guy on the thread below:

    http://dberri.wordpress.com/2007/06/04/rocket-science-clemens-and-%E2%80%98roids/

    Perhaps he’s fixed it by now? I don’t have time to check.

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  7. paul says:

    Apropos of Stigler’s study: I recall reading about the non-influence of steroids on performance back in the McGwire controversy. Seems that players take this stuff because they believe it enhances their performance; i.e., taking steroids is a superstition, like not stepping on the foul line when running to or from the dugout. If a player believes steroids are helping, are they?

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  8. km says:

    ML, studies rarely disprove anything because it’s very hard to prove a negative.

    And if studies show that using steroids doesn’t tend to improve performance, then this analysis is even less likely to disprove that Clemens used PEDs.

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