In any random group of 25 people, there is a very high probability
that two persons in that group will have the same birthday
anniversary. Not born in the same year...just the same anniversary date. I
have forgotten the mathematical proof of this. What is that proof?

Hello knowitall22-ga,

Here is a good explanation of the formula for showing the probability
of finding two people in a group with the same birthday.  The formula
for that probability is 1 - (365_P_n)/(365^n), which can also be
written as 1 - 365! / ((365-n)! * 365^n).  This probability goes above
50% when there are 23 people in the group.

"Ask Dr. Math: FAQ - The Birthday Problem"
The Math Forum @ Drexel
http://mathforum.org/dr.math/faq/faq.birthdayprob.html

The probability is about 56% for a group of 25 people.

"Ask Dr. Math - Birthday Probability, Class of 25" (11/14/2002)
The Math Forum @ Drexel
http://mathforum.org/library/drmath/view/61640.html

I hope that this information is helpful.

- justaskscott-ga


Search terms used on Google:

group "same birthday" probability formula 25

Thanks, justaskscott-ga.