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13 Weeks: Diets and Black Swans


Nassim Nicholas Taleb's book The Black Swan introduced an old term and then, annoyingly, redefined it. For Sir Karl Popper, the black swan was an observation about logical quantification: if you assert "all swans are white" then the observation of a single black swan falsifies the assertion.

Taleb's observation is different, although related: he's observing that really unexpected events are unexpected: we have a model of the world that says "The US mainland is secure from attack" that seems perfectly plausible on 10 September 2001; we believe "Islamist terrorism is on the run" and then a bomb blows up in Boston.

(There's a more sophisticated way to deal with all of these called Bayesian inference. We'll leave the details for a science column, but in a few words, a Bayesian starts with an assumed a priori estimate of the probability of an event. After observation, they have a new a postieriori estimate that incorporates new experience.)

But there's yet a third way to think about these that shows us how mathematics and probability can show us surprising things.

(Yes, this is a diet and exercise column, just a little further down.)