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Topic: Birthday Paradox (Read 594 times) |
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Milena
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Hmmm not sure about this one. It really is a paradox!
Let's say there are 364 days in a year (adding up all the days in each month of a regular year). If there are 2 people in the room the probability of them having the same birthday is 1/364.
If there are 3 people, the probability is 3/364.
For 4 people the probability is 6/364
In general the probability of 2 people having the same birthday in a room of n people is [n(n-1)/2]/364
Thus to get a probability of over 50%: [n(n-1)/2]/364 = 0.5
n = 20 people.
Do you agree?
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NickH
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Posts: 341
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Re: Birthday Paradox
« Reply #1 on: Apr 5th, 2003, 11:36am » |
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No, I don't agree. For one thing, your formula would indicate that with 28 people the probability is greater than 1! For another, there are 365 days in a (non-leap) year.
There must be a thread for this puzzle already somewhere on the forum. Anyway, try calculating the probability that, with n people in the room, all have different birthdays.
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| « Last Edit: Apr 5th, 2003, 11:37am by NickH » |
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