I was going to say that I was disappointed that the page didn't show the formula for the probability and show how it changes as you change the number of people

I was going to say that I was disappointed that the page didn't show the formula for the probability and show how it changes as you change the number of people in the room. Then I checked the wiki page and understood that some of the maths is actually quite fiendish (for non mathematicians anyway) - https://en.wikipedia.org/wiki/Birthday_problem https://en.wikipedia.org/wiki/Birthday_problem