Study on how the strike zone changes with the count

Here's an interesting article I saw on how the strike zone becomes smaller when the pitcher is ahead in the count and becomes larger when the pitcher is behind in the count. The study is based on data from about 200,000 pitches at various counts, and whether they're being called strikes or balls. Click here for the story.

It's interesting to me that even smack dab in the middle of the strike zone is not 100% strike. I don't watch much baseball anymore, but when I was younger I remember being amazed that some pitches seemingly right down the middle of the plate would be called balls. (The strike zone grids shown don't have probabilities shown, but note that the middle of the plate both vertically and horizontally is not uniformly red - some get called balls.)

Tip to the Marginal Revolution for putting me onto the link.