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Speaker 1: Welcome to brain Stuff production of I Heart Radio. Hi

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Speaker 1: brain Stuff, I'm Lauren Vogelbaum, and this episode is another

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Speaker 1: classic from our erstwhile host, Christian Sager. This one breaks

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Speaker 1: down the conundrum of the birthday paradox, which isn't a

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Speaker 1: true paradox, but rather a thought experiment in probability theory

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Speaker 1: and a good way of demonstrating exactly how bad we

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Speaker 1: humans are at probability math off the top of our heads. Hey,

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Speaker 1: brain Stuff, it's Christian Sager and today's question is what

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Speaker 1: is going on with the birthday paradox. You've probably heard

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Speaker 1: this one before, the idea that if there are twenty

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Speaker 1: people in a room, there's a fifty fifty chance that

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Speaker 1: two of them will have the same birthday. So how

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Speaker 1: can this be? Well, it really is called the birthday paradox,

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Speaker 1: and it turns out it's useful in several different areas,

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Speaker 1: for example, in cartography and hashing algorithms. You can try

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Speaker 1: it yourself the next time you're at a gathering of people. Know,

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Speaker 1: just ask everyone for their birthday. I mean, don't be

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Speaker 1: creepy about it. Play cool, say you know something like

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Speaker 1: I'm trying to prove this for science or whatever, and

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Speaker 1: it's likely that two people in this group will have

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Speaker 1: the same birthday, not around the same time, they will

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Speaker 1: have the exact same day. And this really surprises people.

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Speaker 1: So the reason isn't so surprising. It's because we're used

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Speaker 1: to comparing our particular birthdays with some other individuals particular birthday. So,

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Speaker 1: for example, you meet somebody randomly and you ask her

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Speaker 1: what her birthday is, the chance of the two of

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Speaker 1: you having the same birthday is only one out of

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Speaker 1: three hundred and sixty five, or four point to seven percent.

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Speaker 1: In other words, the probability of any two individuals having

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Speaker 1: the same birthday is low. Even if you asked twenty

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Speaker 1: individual people, the probability is still low, it's less than

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Speaker 1: five percent. It's natural that we feel like it's very

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Speaker 1: rare to meet anybody who has the same aimed birthday

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Speaker 1: as our own. But when you put twenty people in

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Speaker 1: a room, however, the thing that changes is the fact

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Speaker 1: that each of these twenty people is now asking each

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Speaker 1: of the other nineteen people about their birthday simultaneously. Each

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Speaker 1: individual person only has a small chance, less than a

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Speaker 1: five percent chance of success, but everyone's trying it at

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Speaker 1: the same time, and that increases the probability dramatically. So

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Speaker 1: the next time you're with a group of twenty or

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Speaker 1: thirty people, why not give it a try. You might

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Speaker 1: be surprised. Today's episode was written by Ben Bolan and

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Speaker 1: produced by Tyler Clang. Brain Stuff is production of I

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Speaker 1: Heart Radios has to Works. For more andes and lots

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Speaker 1: of other mathmagical topics, visit our home planet has toff

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Speaker 1: works dot com. Plus for more podcasts for heart Radio,

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Speaker 1: visit the iHeart Radio app, Apple Podcasts, or wherever you

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Speaker 1: listen to your favorite shows.