> What is the probability that you are sharing the same birthday with people around you?
> What if I told you that in a room with only 23 people there’s already a 50% chance for two of them to have matching birthdays?
I guess it's the subject shift from _you_ to _any two people from a group_ that creates the surprise in the birthday paradox. You definitely need way more than 23 randomly sampled people to get to a high probability that _you_ specifically share a birthday with one of them, and the result does not contradict that notion.
Sup-par phrasing is a subtle advantage of non-AI generated text. In the past, I would be put off by this bad phrasing and the typo ("requier") in the text, but these days, it's a signal that a human took the time to write this, which makes me happy to see.
Any RNG with a period 2**32 that can output every 32-bit value at least once must have zero collisions for the first 2**32 outputs, but we would expect to see about 100 collisions after just 200k outputs.
> What is the probability that you are sharing the same birthday with people around you?
If you're a twin and your twin sibling is standing next to you, nearly 100%. But not exactly 100%: there have been cases of twins born on either side of midnight ending up with birthdays that differ by a day. (I don't personally know of any twins born on either side of midnight between Dec 31st and Jan 1st, who would then have different calendar years in their birthdays, but odds are very good that it has happened at least once in human history).
Or (more likely since most airlines won't let a nine-month pregnant woman on board), born aboard a ship. (These days, most likely a cruise ship).
For extra fun, have them be born on opposite sites of the International Date Line, crossing west-to-east so that the younger twin (born on the east side of the line) is born on (say) July 1st at 8:00 AM local time, while the older twin (born fifteen minutes earlier on the west side of the line) is born on July 2nd at 8:45 AM local time.
For extra EXTRA fun, have them be born on opposite sites of the International Date Line on opposite sides of midnight, AND as the calendar ticks over from Dec 31st to Jan 1st. It gets really, really confusing. Though thankfully, I would bet money that particular example is contrived enough that it has never happened in real life.
> What is the probability that you are sharing the same birthday with people around you?
> What if I told you that in a room with only 23 people there’s already a 50% chance for two of them to have matching birthdays?
I guess it's the subject shift from _you_ to _any two people from a group_ that creates the surprise in the birthday paradox. You definitely need way more than 23 randomly sampled people to get to a high probability that _you_ specifically share a birthday with one of them, and the result does not contradict that notion.
Sup-par phrasing is a subtle advantage of non-AI generated text. In the past, I would be put off by this bad phrasing and the typo ("requier") in the text, but these days, it's a signal that a human took the time to write this, which makes me happy to see.
..or is it "sub-par"?
I didn't even notice it at first!
This is also an easy way to detect RNGs that are not truncated (i.e. return the entire state (or any 1-to-1 permutation of their entire state):
https://www.pcg-random.org/posts/birthday-test.html
Example:
Any RNG with a period 2**32 that can output every 32-bit value at least once must have zero collisions for the first 2**32 outputs, but we would expect to see about 100 collisions after just 200k outputs.
Such an RNG would be great for playing your 2^32 song collection, since you'd never hear the same song twice within a given time through.
> What is the probability that you are sharing the same birthday with people around you?
If you're a twin and your twin sibling is standing next to you, nearly 100%. But not exactly 100%: there have been cases of twins born on either side of midnight ending up with birthdays that differ by a day. (I don't personally know of any twins born on either side of midnight between Dec 31st and Jan 1st, who would then have different calendar years in their birthdays, but odds are very good that it has happened at least once in human history).
twins born mid flight as plane crosses time zone, can the second twin be born before the first!!?
Or (more likely since most airlines won't let a nine-month pregnant woman on board), born aboard a ship. (These days, most likely a cruise ship).
For extra fun, have them be born on opposite sites of the International Date Line, crossing west-to-east so that the younger twin (born on the east side of the line) is born on (say) July 1st at 8:00 AM local time, while the older twin (born fifteen minutes earlier on the west side of the line) is born on July 2nd at 8:45 AM local time.
For extra EXTRA fun, have them be born on opposite sites of the International Date Line on opposite sides of midnight, AND as the calendar ticks over from Dec 31st to Jan 1st. It gets really, really confusing. Though thankfully, I would bet money that particular example is contrived enough that it has never happened in real life.
And what are the odds of your birthday being exactly at the center of the (non-leap) year? That's my B'day. Cool!
50/50. Either it is or it isn’t!
Related today:
Ask HN: We just had an actual UUID v4 collision...
https://news.ycombinator.com/item?id=48060054
That might be why the OP posted it.