Simple statistical question

1. Jan 28, 2006

Arbu

2. Jan 28, 2006

0rthodontist

Well, the chance of each individually being right is 1/365 (ignoring leap years and assuming people's guesses are independent of the person's actual birthday, which is probably not true), and if they are independent then it follows the binomial distribution, so the answer is
C(408, 13) * (1/365)^13 * (364/365)^395. Unless you're interested in the probability of at least 13 being right.

Last edited: Jan 28, 2006
3. Jan 28, 2006

Arbu

Sorry, statistics represents a bit of a gap in my education. What is this C function, and how do I calculate it/look it up?

Let's go with exactly 13 of them being right.

4. Jan 28, 2006

ksinclair13

C(n, k) = $$\frac{n!}{(k!)(n-k)!}$$

Last edited: Jan 28, 2006
5. Jan 28, 2006

Arbu

Thanks. 1 in 5,370,675,393 I make it.