## The birthday paradox

Take a group of 23 people. What is the probability that two of them share the same birthday? Or let’s take a different approach. How many people do you need to make sure that the probability that two of them share the same birthday is close to 100%? On first glance, 367 seems like a probable answer (as there as 366 days during a year including February 29th). But while you would need as many to get to exactly 100%, you need much less to reach 99% probability.