WEBVTT - BrainStuff Classics: What Is the Birthday Paradox?

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<v Speaker 1>Welcome to brain Stuff production of I Heart Radio. Hi

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<v Speaker 1>brain Stuff, I'm Lauren Vogelbaum, and this episode is another

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<v Speaker 1>classic from our erstwhile host, Christian Sager. This one breaks

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<v Speaker 1>down the conundrum of the birthday paradox, which isn't a

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<v Speaker 1>true paradox, but rather a thought experiment in probability theory

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<v Speaker 1>and a good way of demonstrating exactly how bad we

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

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<v Speaker 1>brain Stuff, it's Christian Sager and today's question is what

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<v Speaker 1>is going on with the birthday paradox. You've probably heard

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<v Speaker 1>this one before, the idea that if there are twenty

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<v Speaker 1>people in a room, there's a fifty fifty chance that

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<v Speaker 1>two of them will have the same birthday. So how

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<v Speaker 1>can this be? Well, it really is called the birthday paradox,

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<v Speaker 1>and it turns out it's useful in several different areas,

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<v Speaker 1>for example, in cartography and hashing algorithms. You can try

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

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

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<v Speaker 1>creepy about it. Play cool, say you know something like

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<v Speaker 1>I'm trying to prove this for science or whatever, and

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<v Speaker 1>it's likely that two people in this group will have

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<v Speaker 1>the same birthday, not around the same time, they will

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<v Speaker 1>have the exact same day. And this really surprises people.

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

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<v Speaker 1>to comparing our particular birthdays with some other individuals particular birthday. So,

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<v Speaker 1>for example, you meet somebody randomly and you ask her

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<v Speaker 1>what her birthday is, the chance of the two of

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<v Speaker 1>you having the same birthday is only one out of

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<v Speaker 1>three hundred and sixty five, or four point to seven percent.

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<v Speaker 1>In other words, the probability of any two individuals having

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<v Speaker 1>the same birthday is low. Even if you asked twenty

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<v Speaker 1>individual people, the probability is still low, it's less than

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<v Speaker 1>five percent. It's natural that we feel like it's very

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<v Speaker 1>rare to meet anybody who has the same aimed birthday

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<v Speaker 1>as our own. But when you put twenty people in

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<v Speaker 1>a room, however, the thing that changes is the fact

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<v Speaker 1>that each of these twenty people is now asking each

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<v Speaker 1>of the other nineteen people about their birthday simultaneously. Each

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<v Speaker 1>individual person only has a small chance, less than a

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<v Speaker 1>five percent chance of success, but everyone's trying it at

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<v Speaker 1>the same time, and that increases the probability dramatically. So

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<v Speaker 1>the next time you're with a group of twenty or

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<v Speaker 1>thirty people, why not give it a try. You might

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<v Speaker 1>be surprised. Today's episode was written by Ben Bolan and

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<v Speaker 1>produced by Tyler Clang. Brain Stuff is production of I

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<v Speaker 1>Heart Radios has to Works. For more andes and lots

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<v Speaker 1>of other mathmagical topics, visit our home planet has toff

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<v Speaker 1>works dot com. Plus for more podcasts for heart Radio,

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