Birthday Paradox: How many people do we need to have a 50-50 chance of at least two people sharing the same birthday? Only 23.
Article: The Birthday Paradox Experiment
Counterintuitively, in a room of only 23 people, the probability of at least two people sharing the same birthday is over 50 percent. Also, it only needs 60 people in a group to make sure that there’s a 99% chance of at least people having the same birthday. You can look up Wikipedia for a more detailed explanation or The Pudding to learn through an interactive experiment.
Thanks to Professor Juels for teaching this interesting paradox and Angelica Kosasih for sharing The Pudding website.