from Amazon
Tuesday, October 18, 2011
Outcomes by fastball speed
Jeff presents some interesting data.
This is a perfect example of a sampling bias. While it looks like this is a complete population of pitchers, the reality is that the MLB pitchers is a sample of all pitchers. Notably, if your fastball speed is below 90mph, then the only way to be a MLB pitcher is to be able to do something else well (location, movement, other pitches, etc).
Ultimately, the bias is so strong as to render the data presented as applying only to those pitchers who happen to be in MLB, and you can’t apply it to all pitchers who throw at that speed.