Birthday problem was a Natural sciences good articles nominee, but did not meet the good article criteria at the time. There may be suggestions below for improving the article. Once these issues have been addressed, the article can be renominated. Editors may also seek a reassessment of the decision if they believe there was a mistake.
Article milestones Date Process Result October 1, 2007 Good article nominee Not listed

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I just noticed this, which I don't see in the article: ${\displaystyle {\frac {\log(1/2)}{\log(364.25/365.25)}}\approx 252.83\approx {\binom {23}{2}}}$ —Tamfang (talk) 18:01, 28 March 2024 (UTC)Reply

So what? --Macrakis (talk) 20:37, 28 March 2024 (UTC)Reply

364.25/365.25 is the probability that a given pair do not share a birthday. 253 is the number of pairs among 23 people. I never knew before why the threshold number is 23. —Tamfang (talk) 06:15, 29 March 2024 (UTC)Reply

So you're saying that this is more than a coincidence? --Macrakis (talk) 15:45, 29 March 2024 (UTC)Reply

Much closer, but equally meaningless: 365*log(2) = 252.999. --Macrakis (talk) 21:17, 28 March 2024 (UTC)Reply

Or to put that another way, 23 is the smallest integer n such that ${\displaystyle ({\frac {364.25}{365.25}})^{\binom {n}{2}}\leq {\frac {1}{2}}}$. —Tamfang (talk) 00:03, 30 March 2024 (UTC)Reply

OK, I think I'm beginning to follow you here. Small detail: article says that leap years aren't taken into account, so it should be 364/365. --Macrakis (talk) 15:08, 1 April 2024 (UTC)Reply

Taking that further, the approximation n >= 0,5 + sqrt(0,25 + 2 * ln(2) * 365) mentioned in the article could then be improved by writing it as n >= 0,5 + sqrt(0,25 + 2 * ln(2) / ln (365/364)) Roelgrif (talk) 02:16, 11 January 2025 (UTC)Reply

There are no examples here of real life tests. Like going into a classroom or office and asking people. If this is just a numbers game it should be made clear at the start. 2A00:23C8:E414:1F01:6D85:5817:D045:A7F3 (talk) 23:16, 10 April 2025 (UTC)Reply

The article makes clear that it's about probability. The article also later mentions real-world probability due to unneven distribution.  …/NemoThorx (💬 • 📜) 11:35, 4 August 2025 (UTC)Reply

Any real life test would be original research. The point is that it doesn't need a real life test, because it's a mathematical concept. All you need is a piece of chalk.User:Pedant (talk) User:Pedant (talk) 03:13, 10 January 2026 (UTC)Reply

Hi all. I've been on an interactivity kick lately, given the possibilities opened by the new {{calculator}} template, and spent some time figuring out an interactive version of the birthday problem for the article. Disclosure: I used Claude Code to make the calculator syntax more manageable. This one's been through several versions at this point, trying to make it the most useful. I still have ambitions to replace the random dates with a random list of notable people (see this VPT thread), but it's usable as-is. What do we think? Worth adding? — Rhododendrites ^talk \\ 22:45, 30 July 2026 (UTC)Reply