The Birthday Paradox

jee · Post by **jee** » 12 Feb 2006, 10:25

if you're sitting in a room with forty people in it, what are the chances that two of those people have the same birthday?... 11% ? 22% 75% hmmmmmm

what thinkest tho, oh great matematicians?

Supreem1 · Post by **Supreem1** » 12 Feb 2006, 10:35

1 in 3.1025199175256222200663620323336e+102

or something along those lines

Slasher · Post by **Slasher** » 12 Feb 2006, 10:38

Now If I wasnt so lazy Id take out my Analytical Techniques handbook and give you the formulae... Its quite easy, but sooo much work

jee · Post by **jee** » 12 Feb 2006, 10:45

cum on Slash, this is meant to get that creative juices going.....

Slasher · Post by **Slasher** » 12 Feb 2006, 10:53

wouldnt it be like 1/365 * 1/365 ... x 40 ?

I hated ATE , so not going to go into the book hunt now... dont even know where it is anymore...

Post by **Y0da** » 12 Feb 2006, 11:24

Well if you considder that there are 365 possible birthdays then the odds for any 2 people to share the same birthday would probably be 365 to 1. However if you have 40 people the odds should increase by the amount of people devided by 2. Thus I would say 365 to 20 or 5.48%.

Slasher · Post by **Slasher** » 12 Feb 2006, 16:04

What are the odds then of all 40 people sharing that birthday y0da?

I dont quite understand the logic...

There is a standard formuale for throwing a dice and getting same number twice... This is just a 365 sided dicce (Unless you count leap years) and you roll 40 times...

Post by **Y0da** » 12 Feb 2006, 16:14

Well if you take in consideration the fact that 2 people have a 1 in 365 chance to share the same birthday then 4 people would have a 2 in 365 chance and 40 people a 20 in 365 chance. This is just pseudo logic of course and not based on any formulas.

Edit - The above is for 2 people in a crow of 40. To find the chance for all 40 to share the same birthday I would guess you could devide the odds by the number of people. So it would then be 365 to 1/40 or 0.007%

Post by **Thrall** » 12 Feb 2006, 16:51

Post by **Y0da** » 13 Feb 2006, 14:13

Thrall wrote:50%

What, either they do or they don't?