Simple Birthday Probability Question
 

In a group of 10 people what's the probability someone shares my birthday? Thanks.

Re: Simple Birthday Probability Question
 

Assuming you weren't born on Feb. 29, the prob. is:
1 - (364/365.25)^10 = 3.37%

Re: Simple Birthday Probability Question
 

However, if you wish to complicate things, you could take into account the fact that more people are born on certain days, for example Sept. 30 (champainge baby).

But I don't.

Re: Simple Birthday Probability Question
 

I am trying to relearn/reunderstand probabilities and I know the easiest way to do it is as slickpoppa did, subtrace the probability none share the same birthday from 1.

Just out of curiousity, and I don't need you all to spend any time actually doing it, would I be correct to assume it would be very hard to do it the long way by pen and paper?

How would you do it, compute the chance of exactly two having the same birthday, then exactly three etc?

Probably a basic question but it is what it is.

Re: Simple Birthday Probability Question
 

The "long" way is as follows:
Chance of x people people having same birthday as you:
(1/365.25)^x * (364/365.25)^(10-x) * [10!/(x!*(10-x)!)]
Then you sum the above equation for x = 1,2,3,....

Re: Simple Birthday Probability Question
 

Thanks for this. I will have to think about it for a bit. You have a big brain!

Re: Simple Birthday Probability Question
 

This is not true if your birthday is Feb 29. [img]/images/graemlins/smile.gif[/img]