The birthday problem
David Kessler and Jeremy Schiff
This paper was never intended for publication. It deals with the
famous "birthday problem": Assume there are D days in a year,
and there is equal probability of being born on any particular day of the year.
What is the probability
that in a group of N people (with N no bigger than D) there are (at least)
two with the same birthday? We wrote up this paper as supplementary
reading for the students in our probability courses, but since it might
be of wider interest I am posting it here too.