Canconda’s original comment did not have the wiki link which is why I replied. Honestly, dropping 23 possible birthday pairs to reach >50% probability is still not intuitive to me.
Of my OG friend group of ~12 there are two matching birthday pairs. One coincidental and one pair of twins which don’t count.
With the first person, you have 1/365 chance the birthday will be on any given day.
Each person you add to that adds not just another person but also another day that can be a match.
After two people, you still don’t have a match but now you have two days. The third person can match either of those. That’s a lower bar than person #2 had to meet.
After 15 people, the question is: “what are the odds that any two of you share any of these 15 days as your birthday.”
See how this already sounds a little more likely than just narrowing in on “have the same birthday?” When it’s said that way it sounds like more of a bullseye than it truly is.
So I think part of it is difficult to grasp intuitively, but it’s also phrased deliberately to throw off your intuition.
Canconda’s original comment did not have the wiki link which is why I replied. Honestly, dropping 23 possible birthday pairs to reach >50% probability is still not intuitive to me.
Of my OG friend group of ~12 there are two matching birthday pairs. One coincidental and one pair of twins which don’t count.
To grasp it intuitively, I think of it like this.
With the first person, you have 1/365 chance the birthday will be on any given day.
Each person you add to that adds not just another person but also another day that can be a match.
After two people, you still don’t have a match but now you have two days. The third person can match either of those. That’s a lower bar than person #2 had to meet.
After 15 people, the question is: “what are the odds that any two of you share any of these 15 days as your birthday.”
See how this already sounds a little more likely than just narrowing in on “have the same birthday?” When it’s said that way it sounds like more of a bullseye than it truly is.
So I think part of it is difficult to grasp intuitively, but it’s also phrased deliberately to throw off your intuition.