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An analog of the birthday paradox that gets me all the time is what I think of as The Locker Room Paradox. This is where when I go into the locker room after working out and the guy who comes in behind me ends in the locker right next to mine. So there’s two of us in a big empty room awkwardly jostling away.

I really like the fact that it's using the previous user birthdays. Unfortunately today is my birthday and I think a lot of people are entering today's date as their birthday, I got 6 matches... :)

I'm a bit confused. Maybe i did not pay enough attention but... Does it stop the first simulation when there are _any_ 2 people with a same birthday, or when someone has _my_ birthday? I think the latter will take more people on average.

I was going to try it again with February 29th

It's interesting how uniform the birthday distribution at the end looks. I'd expect more seasonality (e.g. more babies conceived in the cold, dark months).

Okay, that was about as clear as mud to me. Maybe I just need more coffee, but nothing about it led me to understand why there is a 50% chance with 23 people. Can someone else explain this?

The odds that someone else shares just your birthday out of 23 people sounds crazy still. It should be 182.5 to get to 50%, right?

I had a hard time believing the birthday paradox when I first heard about it years ago, so I modeled it with Clojure/Incanter and the results were spot on. Really interesting and fun paradox.

Incredible site that also is very mobile friendly!

Aren't there birthdays that are more likely than others?

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

While the math is clear, I'm a bit annoyed by the label "paradox" as the whole setup is too simplistic and reductionistic.

The actual chance of being in the same room with someone who shares your birthday needs to include other factors like your socioeconomic background, the cultural environment you are in, your present location, and certain historical facts.

Without having done the math, I'm fairly certain that a member of the baby boomer generation in New York has a higher chance of meeting their birthday sibling than a 12-year-old in a rural part of Australia.

(2018)

Scripted.