Ask HN: The Birthday Problem

1 pointryanthedev4 comments

What's the probability of two people sharing the exact birthday? (dd-mm-yyyy)

It is similar to the problem of grocery checkout. If there are n checkout lines, the probability of being in the quickest line is 1/n, assuming that all checkouts have lines.

It is probably 1/(how many possible birthdays in a given year range). To be conservative (90 years): 1/90*365 or 0.003%.

Is 90 years the representation of the average age of a person?

What if it didn't matter that they were alive or dead?

Meaning I have a hat with every name and birthday of every "human". Every time someone is born, their name is added to the hat. Essentially an infinite set of names would be added.

What's the probability when N is infinite? Like a grocery store with an infinite amount of checkout lines.

1) Open browser

2) Navigate to https://duckduckgo.com/

3) Type in "!w birthday problem" (without the quotes)

4) Read the wikipedia page that appears

Thanks! I scoured the wiki. Didn't find any examples of using an infinite set. Could you be a bit more specific? It's definitely possible I missed the section.

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