If you take a group of people born in a non leap year you would need 366 people for a 100% chance that someone shares a birthday but only 23 people for a 50% chance that somebody shares a birthday?
In: Mathematics
You’re thinking about comparing Person 1 to everyone else and looking for a match, but that’s not it.
You’re comparing Person 1 to People 2 – 23…and then *also* comparing Person 2 to People 3 – 23…and then *also* comparing Person 3 to People 4 – 23…and then *also* comparing Person 4 to People 5 – 23…and then *also…*
It ends up being a much, much, much larger amount of combinations than you thought it was.
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