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#1 2008-12-10 11:47:56
- Hazzy
- Member
- Registered: 2008-12-10
- Posts: 2
People's Birthdays.
My Stats teacher likes to talk... a lot.
Apparently, if you have 23 people in a room, group, or something, there's a 50% chance at least two of them share a birth Day and Month.
(Yey, I think it worked.)
Ends up being:
364/365 * 363/365 * 362/365 * 361... 341/365 = .5
Fractions are fun in large quantities. 
Last edited by Hazzy (2008-12-10 12:05:59)
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#2 2008-12-10 12:26:47
- mathsyperson
- Moderator
- Registered: 2005-06-22
- Posts: 4,900
Re: People's Birthdays.
It's not exactly half though. It's that 23 is the lowest amount of people you need in a room for a birthday-match existing to be more likely than one not existing.
Still fairly incredible though. Most people would estimate a number far higher.
Why did the vector cross the road?
It wanted to be normal.
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