Birthday celebration The birthday problem is a question in probability theory that asks, “What is the probability that at least two people in a given a group of n people share the same birthday?” (For the group of eight people shown here, the probability of two of them having the same birthday is about 0.07, or 1 in 13.) (more) birthday problem probability theory Actions Share Share Share to social media Facebook X URL https://www.britannica.com/science/birthday-problem Share Share Share to social media Facebook X URL https://www.britannica.com/science/birthday-problem Also known as: birthday paradox Written by Michael McDonough Michael McDonough was a media team intern at Encyclopaedia Britannica. He is expected to graduate in 2023 from Northwestern University. Michael McDonough Fact-checked by The Editors of Encyclopaedia Britannica Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. They write new content and verify and edit content received from contributors. The Editors of Encyclopaedia Britannica Last Updated: Oct 3, 2024 • Article History Table of Contents Also called: birthday paradox (Show more) Ask the Chatbot a Question Ask the Chatbot a Question birthday problem, question in probability theory that asks in a group containing a given number of n people, what is the probability that at least one pair of people share the same birthday. The problem is famous for its counterintuitive outcomes, as only a small number of people are needed for there to be a probable chance of a shared birthday—in a group of 23 people, there is an approximately 50 percent chance that two people will share a birthday. Although there is debate over who came up with the original birthday problem, a version was first published by Austrian ...(100 of 1012 words)

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