Sullivan: Stolen-base success against pitch speeds and pitch heights

From Jeff Sullivan at FanGraphs on February 19, 2014:

The other day I tried to sate my own curiosity by looking at what happens to the called strike zone when there’s a runner on the move. The results supported what I expected to be the case, but the data’s also incomplete, so it’s not like anything could be proven one way or another. Ultimately it turned out to be half study and half idea-introduction. There’s not a lot I can do about it now.

The post was powered by the searchable Baseball Savant, which somewhat recently added a “stolen base attempt” check box. This time around, I want to do something a little more obvious with the data, since it’s data I’ve never played with before. There’s information for more than 14,000 stolen-base attempts in the past four seasons, which doesn’t cover all the stolen-base attempts, but does cover most of them. Let’s assume, for the moment, the data that’s available is accurate. How do stolen-base rates change by pitch velocity? How do stolen-base rates change by pitch height? Do the trends follow the patterns we’d expect?

I probably shouldn’t need to tell you the patterns we’d expect. In theory, success rate goes down the faster the pitch. In theory, success rate goes down the higher the pitch (to a point). We might as well just dive into the numbers.

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Originally published: February 19, 2014. Last Updated: February 19, 2014.