Posts in category probability

Birthday Paradox on steroids.

Most of us are familiar with the so-called Birthday Paradox: the probability in a group of 23 people there are (at least) two who share a birthday is larger than 50%. If you are not familiar with this result then you could peek at the calculation on the Wikipedia page or try it for yourself (big hint calculate the probability that no two people in the group share a birthday).

In Act One of Episode 630 of This American Life we see another take on this phenomenon. It occurs in the context of voter fraud, in particular double voting. In this case, a bit simplified, one looks at the probability that in the group of American Voters two of them would have the same name and the same birthday (including the year).

Listen to the episode to see that basically all cases of `double voting’ can be accounted for by chance alone. And then you may want to read the paper on which the item was based, and visit the website of Sharad Goel (who was featured in the broadcast).

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