Still random after all these years?

When Philip Humber of the Chicago White Sox pitched a perfect game against the Seattle Mariners back in April, I wrote that the frequency of these exceedingly rare feats had ramped up dramatically over the last three decades.

Mathematicians argued that speedup was more apparent than real, a classic example of a Poisson distribution. This is the natural tendency for exceptionally rare but random events to bunch up in ways that appear non-random.

Humber’s flawless game was the 19th in modern baseball’s 112-year* history. Since April, there have been two more, including the 1-0 gem Félix Hernández of the Seattle Mariners pitched against the Tampa Bay Rays last night.

Here’s the latest chart:

True, there are more ballgames per year than there were 60 years ago—almost twice as many.

Still, from 1901 to 1960, there was only one perfect game every 15 years. From 1980 to Wednesday night, there was one every 2.36 years.

Random or not, there’s one thing I’m sure Félix Hernández can agree on:

Bayesian ball’s been bery bery good to me.

* Baseball is older than 112, but the rules were so different in the Nineteenth Century, most scholars date the modern era from 1900.

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