Check your intuition: The birthday problem - David Knuffke
View full lesson: http://ed.ted.com/lessons/check-your-intuition-the-birthday-problem-david-knuffke Imagine a group of people. How big do you think the group would have to be before there's...
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Imagine a group of people. How big do you think the group would have to be before there's more than a 50% chance that two people in the group have the same birthday? Assume for the sake of argument that there are no twins, that every birthday is equally likely, and ignore leap years. Take a moment to think about it. The answer may seem surprisingly low. In a group of 23 people, there's a 50.73% chance that two people will share the same birthday. But with 365 days in a year, how's it possible that you need such a small group to get even odds of a shared birthday? Why is our intuition so wrong? To figure out the answer, let's look at one way a mathematician might calculate the odds of a birthday match. We can use a field of mathemat...
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Imagine a group of people. How big do you think the group would have to be before there's more than a 50% chance that two people in the group have the same birthday? Assume for the sake of argument that there are no twins, that every birthday is equally likely, and ignore leap years. Take a moment to think about it. The answer may seem surprisingly low. In a group of 23 people, there's a 50.73% chance that two people will share the same birthday. But with 365 days in a year, how's it possible that you need such a small group to get even odds of a shared birthday? Why is our intuition so wrong? To figure out the answer, let's look at one way a mathematician might calculate the odds of a birthday match. We can use a field of mathemat...
