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Boy or girl paradox

paradox in probability theory

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Record originEnglish Wikipedia
Text licenseCC BY-SA 4.0
Source revisionSep 21, 2026
Entity authorityQ2271174 ↗
Source-derived summary

The boy or girl paradox surrounds a set of questions in probability theory, which are also known as the two children problem, Mr. Smith's children and the Mrs. Smith problem. The initial formulation of the question dates back to at least 1959, when Martin Gardner featured it in his May 1959 "Mathematical Games column" in Scientific American. He phrased the paradox as follows:

Mr. Jones has two children. The older child is a girl. What is the probability that both children are girls?

Mr. Smith has two children.

Editorial summary

The public source identifies “Boy or girl paradox” as paradox in probability theory. This brief keeps that definition visible, then builds a research path around girl, paradox and probability.

Editorial reviewA dependable orientation record for establishing vocabulary, names and a first evidence trail. The current lead gives the account dated anchors—1959—that can be checked directly. The selected authority fields contribute no independent date. Its value is orientation rather than verdict, with girl, paradox and probability providing the first useful test.
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Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Sep 21, 2026. The linked authority identifier is Q2271174. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1959.

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Source & attribution

This entry incorporates text from “Boy or girl paradox” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.