Talk:Birthday problem

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Former good article nominee Birthday problem was a Natural sciences good articles nominee, but did not meet the good article criteria at the time. There are 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.
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Historical inaccuracy[edit]

The article says that:

"The history of the problem is obscure, but W. W. Rouse Ball indicated (without citation) that it was first discussed by an "H. Davenport", possibly Harold Davenport.[2]"

However, looking at quote [2] which is available through the Gutemberg project, there is no reference to the problem or to "H. Davenport". In addition due to the life span of Davenport and the time when the book was written it is unlikely that he proposed the problem.

Looking further, the problem was apparently stated by Richard Von Mises (http://en.wikipedia.org/wiki/Richard_von_Mises) in:

Cf. R. von Mises, Ueber Aufteilungs- und Besetzungswahrscheinlichkeiten, Revue de la Faculté des Sciences de l'Université d'Istanbul, N. S. vol. 4 (1938-1939), pp. 145- 163.

This is info was taken from: Feller, W. (1968). An Introduction to Probability Theory and Its Applications (Vol. 1). Wiley. Third ed., pp. 33.

The German wikipedia entry on the birthday problem indicates that: The paradox is often attributed to Richard von Mises . According to Donald E. Knuth , this origin is not certain : The birthday paradox has been discussed informally among mathematicians as early as the 1930s , but a more accurate copyright can not be determined.

160.228.81.206 (talk) 14:39, 7 March 2014 (UTC) Andrés Altieri

  • Gutenberg is serving the 1905 reprint of the 4th edition because it is the latest version that is in the public domain. This book was first published in 1892 and went through many revisions. The quote about "H. Davenport" is in the 1960 edition (which is not public domain) on page 45 – please have a look. As I said, it is not referenced, nor is the full name given. However, Ball is certainly reliable and therefore quotable. I think the history is obscure, and perhaps it is worth a new sub-section in the body (something like "Origin of the Problem") which talks about the various claims of priority. Our article on Richard von Mises does indeed assert he posed the problem, but the source is a non-WP:RS website. I certainly would welcome any additional information that could be found and reliably sourced, and I think readers would, as well. Agricola44 (talk) 16:11, 7 March 2014 (UTC).
  • I've checked Feller and he does indeed reference the von Mises paper for his discussion of the birthday problem, although he does not say von Mises originated the problem. What is the Knuth reference you referred to? Agricola44 (talk) 17:10, 7 March 2014 (UTC).
  • I am Harold Davenport's son, and family legend has it that he and Coxeter discovered it by noting that two people dining at Trinity had the same birthday. This would have been after Rouse Ball's death, though, and I do not know what the history of the 1960 printing of Rouse Ball's book is. JamesHDavenport (talk) 23:45, 8 March 2014 (UTC)
  • Yes, Ball died in 1925, when the book was in its 9th or 10th edition, and Coxeter continued to develop and add to the content of later editions/reprints. The assertion very likely came from him. This may be one of those occasions where there are competing claims of priority, all the more reason to have a new section on "Origin of the Problem". Do you know of any source that confirms your family legend? Thanks, Agricola44 (talk) 15:55, 10 March 2014 (UTC).

Non-mathematical explanations?[edit]

Maybe couples tend to have sex more often during certain parts of the year(New Year, for instance), and therefore, birthdays tend to be more common around the fall. JDiala (talk) 05:22, 11 January 2014 (UTC)

Perhaps, but for the purposes of this article, distribution of birthdates has been ignored. Per the text, "These conclusions include the assumption that each day of the year (except February 29) is equally probable for a birthday." Mindmatrix 15:05, 11 January 2014 (UTC)

Is it weird?[edit]

Is it a coincidence, that the sum of numbers 1..22 (i.e. one less than 23 people required for 50% chance to have any birthday match) equals 253, which is the number of people required to have 50% chance of a match for any particular person?

It would follow that the first of the 23 people has 22 chances for a match, the second one has 21 chances and so forth, hence 22+21+..+1+0. — Preceding unsigned comment added by 89.69.165.161 (talk) 21:37, 29 August 2014 (UTC)