NAMISHA GUPTA - 023

    The Birthday Paradox is a well known statement of probability theory. It deals with the probability that, in a set of n randomly chosen people, some pair of them will share the same birthdays.

     The problem is originally defined as the probability of any two people in the room sharing the same birthday. The key point is that any two people in the room could share a birthday. People tend to naively misinterpret the problem as the probability of someone in the room sharing a birthday with a specific individual, which is the source of the cognitive bias that often causes people to underestimate the probability.

 Example: In a room of just 23 people there’s a 50-50 chance of two people having the same birthday. In a room of 75 there’s a 99.9% chance of two people matching.

    If there are 367 people (excluding the leap year: Feb 29) in a room? What is the probability that 2 of them have the same birthday? The "pigeonhole principle" says that if you keep picking unique birthdays for people in the room, you will run out of unique birthdays before you run out of people. 

 

 Source: http://fob.po8.org/node/90 http://stackoverflow.com/tags/birthday-paradox/info