Wednesday, February 06, 2008

Probability and Sports (Part 1)

I’ve been a lot more aware of probability lately, mostly due to a book I recently read which I’ll talk about some other time. I’ve also noticed some bad uses of statistics and an ignorance of randomness.

I enjoy the show SportsScience on FSN, where they apply physical sciences to the sports. They have a really cool laboratory for recording physical activity, and they get all-pro athletes on to help test hypotheses. For example, they test which athletes hit harder, how fast Chad Johnson stops (on a dime), if Michael Jordan really “hangs” in midair (no), if a basketball player or a football player jumps further, how much further a warm golf ball goes than a cold one, etc.But, sometimes they get it wrong.

In one episode, they wanted to test which stressors affect free throw shooters the most. They brought in an 80% FT shooter from some college.

They had him shoot 10 free throws at a time. The first round, with no distractions, he shot 9 of 10, or 90%. For the second, they added a crowd of people screaming and clapping noisemakers, some clowns on the court (including one scantily clad female who stayed right in his ear), and some flashing strobe lights. The guy hit 7 of 10, or 70%. Thus, they determined the distractions lowered his shooting by 22.2%.

This, however, is a false conclusion. The average of 90% and 70% (the shooter's 2 scores) is 80%, which is what the guy shoots in real-life (based on a large data set of hundreds of free throws in various situations). You can’t say the distractions had anything to do with his 7 of 10, as this was probably just regression to the mean. See, if you have an 80% free throw shooter shoot sets of 10 free throws, he’s going to hit a range of 6 of 10, 8 of 10, and 10 of 10 sometimes. Scientifically, you can’t take one of those sets and determine anything meaningful about it compared to the others.

Now, if you had him shoot 500 free throws without a distraction and 500 with distractions and compared the results, controlling for all other factors, you might be able to say something.

Next, they had the guy shoot with all the previous distractions, plus a heavy metal band playing louder decibals than the loudest NBA arena. He shot 6 of 10. They concluded that sensitivity to sound must be greater than sight, thus he shot more poorly. Again, a faulty conclusion.

Thankfully, they did make one good insight: They monitored the player's brain activity and heart rate during every exercise. When the heavy metal band started, the player’s heart rate jumped considerably. This might be useful information (if more tests are run on more players).

The scientists say that if you most want to distract a player, make a loud and unexpected noise during a free throw. A bull horn, or a loud clap or something. This should make his heart rate spike and increase his chances of missing (not sure what they were basing this on). So, I hope any Kentucky students reading this will keep that in mind for when Florida comes to Rupp.

But, beware misuse of statistics by people on television.


TaylorW said...

your attention to detail is brilliant. The world needs more of it...

JTapp said...

thanks, Taylor. I appreciate it.