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Birthday paradox - Try this out

Hey there =]

Don't know if you've heard of the birthday paradox, but it basically states that once you reach 57 people in a room there is a 99% chance that they share the same birthday.

So to try this out, just post your birthday and we'll see how many people it takes before a birthday is shared

To start off - June 18th

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Reply 1
Sounds fun! 5th of June.
June 25th
Reply 3
Reply 4
17th September :smile:
Reply 5
Reply 6
5th of September
Reply 7
3rd march
9th September

In the do you share your birthday with a famous person thread, within 2 pages there were 2 other people with my birthday (and exact birthdate!) and at least 2 other pairs of shared birthdays.


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Reply 9
Original post by 1992LP
Sounds fun! 5th of June.


so close! 6th of june
23rd january

Anyone?
28th of June, anyone?
Reply 12
21st November
Reply 13
31st of dec
Reply 14
30th August
Reply 15
26th February
Reply 17
Reply 18
30th november
Original post by Andy_J
I have no idea how that works since the odds are 1 in 365 but ill go with it.

30th May


To get a 100% chance of success, you need 367 people due the the 1 in 366 (leap year) probability. However when the probability is under 100%, combinations increase the probability a lot quicker.

2 people, only 1 way in which the birthday can be shared
3 people there are 3 ways
4 people there are 6 ways
5 people there are 10 ways
etc...

and at 57 people, there are 1596 possible combinations!

Hence the high chance at such a low number!
(edited 10 years ago)

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