Everybody has a story about that one witty teacher or professor who totally pulled one over on the class, and one economics professor just went viral with his own little inside joke.

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The unnamed doctor wore a shirt joking, "There are two types of people in this world: 1.) those who can extrapolate from incomplete data." And, if you can't guess the second type, then you might just be one of them.

Twitter user Kimberly Boswell posted a photo of the shirt and wrote that two of her classmates (who apparently can’t extrapolate from incomplete data) asked if the shirt was missing a second part. As a helpful bit of background, “extrapolate” is defined as “to infer from data already known.”

Of course, the internet had a field day poking fun at the students who didn’t get the joke; especially when Kimberly explained that it was a post-graduate economics class.