Baseball, regression to the mean, and avoiding potential clinical trial biases

This post originally appeared on The Timmerman Report. You should check out the TR.

It’s baseball season. Which means it’s fantasy baseball season. Which means I have to keep reminding myself that, even though it’s already been a month and a half, that’s still a pretty short time in the long rhythm of the season and every performance has to be viewed with skepticism. Ryan Zimmerman sporting a 0.293 On Base Percentage (OBP)? He’s not likely to end up there. On the other hand, Jake Odorizzi with an Earned Run Average (ERA) less than 2.10? He’s good, but not that good. I try to avoid making trades in the first few months (although with several players on my team on the Disabled List, I may have to break my own rule) because I know that in small samples, big fluctuations in statistical performance in the end  are not really telling us much about actual player talent.

One of the big lessons I’ve learned from following baseball and the revolution in sports analytics is that one of the most powerful forces in player performance is regression to the mean. This is the tendency for most outliers, over the course of repeated measurements, to move toward the mean of both individual and population-wide performance levels. There’s nothing magical, just simple statistical truth.

And as I lift my head up from ESPN sports and look around, I’ve started to wonder if regression to the mean might be affecting another interest of mine, and not for the better. I wonder if a lack of understanding of regression to the mean might be a problem in our search for ways to reach better health.
Continue reading

Major League Baseball should be all over the quantified self movement

All opinions are my own and do not necessarily reflect those of Novo Nordisk

Baseball players break down.  Their performances fluctuate.  As a group there are some interesting generalities with respect to how pitching, hitting and fielding change with age.  But the error bars are huge.  There are many things we still don’t know about baseball players, about why one prospect hits the ground running and another flames out.  And we also don’t know if there is any way to know, since the task of putting together the skills needed to play major league baseball may be one of the most complex of the major sports, and understanding complexity is hard.

But it seems worthwhile to give it a try.

The Mystery of the Missing Ligament

Let’s talk about R.A. Dickey for a minute.  Not because he’s a highly interesting human being, although he is.  And not because he’s a knuckleballer, which is fun and interesting due to rarity and the entertaining sight of six foot athletes flailing at baseballs traveling with the flight path of a drunken small-nosed bat.  But rather because he was drafted in 1996 in the 1st round by the Texas Rangers, and only during his physical workup was it discovered that he was missing a key ligament in his arm.  The Ulnar Collateral Ligament (UCL), to be exact.  Without which, it is assumed, a pitcher cannot pitch. Continue reading