The birthday paradox (also known as the birthday problem) is the probability that in a room of 23 strangers, there is a 50% (50.7% to be precise) chance of two people having the same birthday. In a room of 75 people that probability increases to 99.9%. The statistical oddity was first discovered by mathematician Richard von Mises in 1939.

This statistical oddity is categorized as a paradox because is counter-intuitive. In general, people use division rather than the compounding power of exponents to solve problems of probability. For example, to figure out what the chances are to toss a coin and get 10 heads in a row, the average person calculates this way: If getting one head is 50%, then getting two heads is 50% divided by two (25%); therefore, getting ten heads in a row must be 50% divided by 10 (5%). But the proper way to calculate this problem is through exponents: .50 to the power of 10, which equals .001.

There is a rather simple formula (*see for further reading*) to determine the chances of two people having the same birthday, but the key is using the power of exponents. But the simplest proof is as a “parlor trick” next time you are at an event of several dozen people. Impress attendees with your mathematical genius.

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For further reading: *Don’t You Believe It* by Herb Reich (2010)

https://betterexplained.com/articles/understanding-the-birthday-paradox/

http://www.teacherlink.org/content/math/interactive/probability/lessonplans/birthday/home.html

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August 9th, 2016 at 10:39 PM

Or you throw off the stats like we do and show up with triplets

August 9th, 2016 at 11:30 PM

Now that’s out-of-the box thinking 🙂