Report: Penn professors' findings contradict Clemens' analysis of career stats

Updated: February 10, 2008, 6:56 PM ET
ESPN.com news services

Was a report released last month by Roger Clemens' agent supporting the Rocket's late-career statistical improvement just smoke and mirrors? An analysis of that report published Sunday says yes.

Clemens' report stated there were examples of aging pitchers improving their statistics. An examination of those conclusions revealed there were several flaws in the methodology, according to a report in The New York Times.

Clemens' agent, Randy Hendricks, shared an 18,000-word statistical report last month to try to explain how a pitcher could improve when most of his contemporaries were slowing down. One of the goals of the report was to dispute the claims of Clemens' former trainer, Brian McNamee, that Clemens took steroids and human growth hormone later in his career.

"Clemens' longevity was due to his ability to adjust his style of pitching as he got older, incorporating his very effective split-finger fastball to offset the decrease in the speed of his regular fastball caused by aging," the Clemens report said.

University of Pennsylvania's Wharton School professors Eric Bradlow, Shane Jensen, Justin Wolfers and Adi Wyner wrote their opinions of Clemens' report in Sunday's editions of The New York Times. The group said that while Clemens accurately used examples of pitchers such as Nolan Ryan, Randy Johnson and Curt Schilling who pitched well late in their careers, Clemens' report "artificially minimizes the chances that Clemens' numbers will seem unusual. Statisticians call this problem selection bias."

Munson: Numbers Game

Four statistics professors from the prestigious Wharton School do not claim to find evidence of Roger Clemens' guilt, but their study shows that there is "no statistical evidence that points to of innocence," writes Lester Munson. Story

The professors also suggested something was amiss with Clemens' statistics.

"Our reading is that the available data on Clemens' career strongly hint that some unusual factors may have been at play in producing his excellent late-career statistics."

Wolfers elaborated on that point to ESPN.com's Lester Munson.

"What [the Clemens camp] said in their report is indefensible as a matter of statistics," Wolfers said. "The statistics do not point to innocence. We are not saying that the numbers show guilt, but we are saying that the statistics show that something unusual happened in Clemens' career as he entered his 30s."

Hendricks Sports Management, which represents Clemens, responded to the Times story on Sunday.

"The purpose of the report is to provide the statistical background of Roger Clemens' career and to correct misconceptions about his career in the public forum," Hendricks said in a statement.

The Penn professors did their own examination of pitchers who had durability similar to that of Clemens, using parameters that included pitchers who started at least 10 games in at least 15 seasons and pitched at least 3,000 innings since 1968. Thirty-one pitchers fell into this group, in addition to Clemens.

Roger Clemens is not like every other pitcher in this group. He is considered perhaps the best pitcher of his generation. The professors make the mistake of thinking that his career arc should look like the arc of every other pitcher in their selected group.

--Hendricks statement on Roger Clemens

The examination focused on comparing two common pitching stats -- ERA and walks plus hits per nine innings -- from those in the sample group to Clemens' numbers.

The professors found Clemens' late-career success was statistically unusual. Most pitchers in this category peaked with their best numbers around the age of 30, while their declines started in their mid-30s -- about the time Clemens has been accused of using performance-enhancing drugs. Clemens has vehemently denied using steroids or HGH.

However, the Penn professors found that Clemens' statistics did the opposite of those of the rest of the sample. They wrote that the Rocket's stats declined as he neared his 30th birthday, then spiked in his late 30s and early 40s.

Clemens' agents disputed the Penn professors' assumptions that the seven-time Cy Young award winner was just like the other pitchers in the sample size.

"Roger Clemens is not like every other pitcher in this group," the Hendricks statement read. "He is considered perhaps the best pitcher of his generation. The professors make the mistake of thinking that his career arc should look like the arc of every other pitcher in their selected group."

The statement added that Clemens' well-noted workout regimen was similar to Ryan's and that much of the Rocket's success late in his career can be attributed to this aspect of his preparation. It also said that just because changes to Clemens' pitching style -- like focusing less on his signature fastball and more on a split-fingered fastball -- can't be quantified does not mean those changes did not impact Clemens' performance.

The professors' account also noted that Clemens' report focused heavily on his ERA during his career. They pointed out that statistic can be heavily influenced by factors other than the quality of the pitcher's performance, including the strength of a team's defense.

Clemens' camp disputed the claim that ERA is not as important in determining the quality of a pitcher's performance and said the Penn professors didn't take into account several major changes in baseball during the sample period.

"The professors make no adjustments for any of the changes that have taken place in baseball over the last forty years, treating every hit and walk exactly the same, despite the lowering of the pitching mound, the tightening of the strike zone, the changes in equipment, the addition of the designated hitter, the introduction of modern ballparks, and other factors that have affected the game over the years," the Hendricks team stated.

While the professors said Clemens' numbers appear unusual, there is no way to link them to steroids or HGH.

"In any analysis of his career statistics, it is impossible to say whether this unusual factor was performance-enhancing drugs," they wrote.

Wolfers added that their study showed there is nothing statistical that points to innocence.

"You cannot use his statistics to prove that he is innocent. It is not statistically possible," he said. "What they are doing is a good example of lying with statistics."

In addition to the publication of their findings Sunday, the Penn professors plan to release a 15-page report that will be available in a few days and will be published in an academic journal on statistics. They plan to use all of Clemens' available pitching statistics.

ESPN.com's Lester Munson and The Associated Press contributed to this report.

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