Why the Plural of Anecdote is not Data

By: , Twitter

A common theme when I see bad science on the TV or internet is the personal testimony pitch – for me, this holds about as much water as a bucket with no bottom, but not everyone knows why anecdotes do not count as evidence. When talking to people about alternative medicine or psychics, I always get told “but it worked for me, how can you explain that?” It can be explained very easily actually – if I went around to a large enough number of people and gave them a vague Barnum statement, or asked them to pick a card and showed them all the same card, a few would guess correctly, and for those people magic has just happened, and they will go and tell their friends about a miraculous handsome man who did the impossible. That is exactly what alternative medicine quacks and psychics do; take credit for an event that is bound to happen eventually if enough chances are given.

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