(This article was originally published at Big Data, Plainly Spoken (aka Numbers Rule Your World), and syndicated at StatsBlogs.)
Steroids continue to plague professional sports. The latest name to fall is Alex Rodriguez, the shortstop/3rd baseball superstar who currently plays for the Yankees. It wasn't long ago that he was considered a "good guy" of the sport. Now, he's a pariah.
In the rush to make Rodriguez the villain, the media continues to miss these two important aspects to the steroids story:
- Anti-doping tests have a huge false-negative problem. I have been talking about this for years. This topic is examined in Chapter 4 of Numbers Rule Your World. Rodriguez never failed any test; he got caught because one of his enablers ratted him (and others) out. His supplier betrayed him because he didn't pay up. All the other suspended players also were ensnared during the investigation of a Florida clinic.
- Statistics is powerful yet limited. Based on looking at the statistical properties of screening tests, I can be sure that lots of dopers are undetected. Under some assumptions, I estimate that 80% of dopers escape unscathed. However, statistics is hopeless at pinpointing which particular players are the dopers. A similar situation arises in Chapter 5 of Numbers Rule Your World (link) regarding cheaters in the Canadian lotteries; it's not hard to show that there are cheaters but it's hard to figure out who. The solution is to use the police or investigators to supplement the statistics. This is exactly how Rodriguez and the Balco crew (before him) got caught.
There is a third story that is completely ignored by the sports media. Ryan Braun was the 2011 MVP who also patronized the same clinic. Braun, unlike Rodriguez, failed a drug test in 2012. He vigorously defended his innocence (like others), and loudly attacked the messenger. Here is one of his now-infamous quotes:
"It hasn’t been easy. Lots of times I wanted to come out and tell the entire story, attack everybody like I’ve been attacked. My name was dragged through the mud. But at the end of the day I recognized what was best for the game of baseball.”
There are a bunch of other quotes here. Braun got off the same way Lance Armstrong got off years ago when he tested positive... by an expensive legal team and a minor technicality.
In Chapter 4 of NRYW (link), I argue that on chemistry alone, the anti-doping tests are configured such that the positive predictive value is very high, meaning if one tests positive, there is a high chance the subject is a doper. The reverse is not true: if someone is a doper, there is actually a low chance the test would come back positive. These two outcomes are linked and reflect the tradeoff of drug testing.
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