First off, leap years are not being considered for this. In fact the year that people are born shouln't be taken into consideration, for simplicity =P.
The basic question is given an input, a single integer representing the number of people in the room (X >= 1). Return the probability that 2 or more people share the same birthday.
The return from the function should be a value between 0 and 1, inclusive. It should also be rounded out to the 10 thousandth decimal point (4 after the decimal point). There should be no trailing zeros included.
*Side note: being my first problem I'm certainly open to critques as far as setting it up, clarity and of course the test suite.