The birthday paradox concerns the probability that, in a set of n randomly chosen people, some pair of them will have the same birthday. In a group of 23 people, the probability of a shared birthday exceeds 50%, while a group of 70 has a 99.9% chance of a shared birthday.

It's an actually counterintuitive phenomenon, which was named as a paradox, while it actually isn't

Curious.. I wonder why 23 people gets to 50% when there's 365 possible days to have a birthday. Maybe birthing patterns or regional consistencies that change possible outcomes?

That is really interesting, though. Thanks for sharing

It's because the layman would normally think that the answer is 365/2, while the answer is much lower since every person is compared with every other person, making the number of possible pairs very large quite fast. It becomes enough to have 23 people in the same room, a number much lower than 365/2.

I think this is why. So three people having currently undetermined birthdays. One person shares theirs let's say it is June 6th. The next person shares theirs and there is a 1/365 chance that theirs is also June 6th.let's say it is not well now when they third person shares their birthday there is a 2/365 chance that it is shared because there is 2 other birthdays. If a fourth shares then it would be a 3/365 a fifth is 4/365 and so on and so fourth. So this means that in a group of 21 people there is 10 people who have a 1/36.5 chance and ten times that is 1/3.65 so even without doing everyone's equally, using a smaller number than most people have, not counting about half the people, and only rounding down there is a 1 in 3.5 chance

Something about June weddings and valentines and st Patrick's days lol

I'm 90% positive without looking it up that there are months with heavier birthrates than others, and therefore more likely pairs from that month will appear in any given sample

What's the birthday paradox

According to wikipedia :

It's an actually counterintuitive phenomenon, which was named as a paradox, while it actually isn't

Curious.. I wonder why 23 people gets to 50% when there's 365 possible days to have a birthday. Maybe birthing patterns or regional consistencies that change possible outcomes?

That is really interesting, though. Thanks for sharing

It's because the layman would normally think that the answer is 365/2, while the answer is much lower since every person is compared with every other person, making the number of possible pairs very large quite fast. It becomes enough to have 23 people in the same room, a number much lower than 365/2.

Ah, that explains it haha

I think this is why. So three people having currently undetermined birthdays. One person shares theirs let's say it is June 6th. The next person shares theirs and there is a 1/365 chance that theirs is also June 6th.let's say it is not well now when they third person shares their birthday there is a 2/365 chance that it is shared because there is 2 other birthdays. If a fourth shares then it would be a 3/365 a fifth is 4/365 and so on and so fourth. So this means that in a group of 21 people there is 10 people who have a 1/36.5 chance and ten times that is 1/3.65 so even without doing everyone's equally, using a smaller number than most people have, not counting about half the people, and only rounding down there is a 1 in 3.5 chance

Something about June weddings and valentines and st Patrick's days lol

I'm 90% positive without looking it up that there are months with heavier birthrates than others, and therefore more likely pairs from that month will appear in any given sample

Smart

Why?

Because it isn't actually a paradox

Explain?