I heard the following story from my topology professor.
A renowned statistician was teaching a course in fundamental probability theory to a group of undergraduates. As expected of an introductory course, he briefly tackled several main principles of probability to give the students a bird’s-eye view of the subject.
One day, he talked about the famous “Birthday Problem”, which states that a room with 23 people is enough to make the probability of two people sharing the same birthday higher than 50 percent (the exact probability is 50.7297 percent) and it would only require 70 people for the probability to become 99.9 percent.
“This is a rather sizable class. So, the odds of two people having the same birthday in this room is huge!” the professor said confidently.
The professor was bemused when the class suddenly burst out laughing. It took some time before their laughter stopped, and he still couldn’t figure out what was funny. Unknown to him at the time, there were two identical twins sitting next to each other in the front row.