The counterintuitive observation that a random group of people needs to have only 23 members before there is a 50% chance of two of them having the same birthday.

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• Birthday problem — In probability theory, the birthday problem, [This is not a paradox in the sense of leading to a logical contradiction, but is called a paradox because the mathematical truth contradicts naïve intuition: most people estimate that the chance is… …   Wikipedia

• Paradox — For other uses, see Paradox (disambiguation). Further information: List of paradoxes A paradox is a seemingly true statement or group of statements that lead to a contradiction or a situation which seems to defy logic or intuition. Typically,… …   Wikipedia

• Birthday — For other uses, see Birthday (disambiguation). Candles spell out the traditional English birthday greeting A birthday is a day or anniversary where a person celebrates his or her date of birth. Birthdays are celebrated in numerous cultures, often …   Wikipedia

• Birthday attack — A birthday attack is a type of cryptographic attack, so named because it exploits the mathematics behind the birthday problem in probability theory. Given a function f , the goal of the attack is to find two inputs x 1,x 2 such that f(x 1)=f(x 2) …   Wikipedia

• birthday attack — noun A method of code decryption which exploits the so called birthday paradox …   Wiktionary

• Ontological paradox — An ontological paradox is a paradox of time travel that questions the existence and creation of information and objects that travel in time. It is very closely related to the predestination paradox and usually occurs at the same time. Because of… …   Wikipedia

• Bootstrap paradox — The bootstrap paradox is a paradox of time travel in which information or objects can exist without having been created. After information or an object is sent back in time, it is recovered in the present and becomes the very object/information… …   Wikipedia

• Skolem's paradox — is the mathematical fact that every countable axiomatisation of set theory in first order logic, if consistent, has a model that is countable, even if it is possible to prove, from those same axioms, the existence of sets that are not countable.… …   Wikipedia

• Common Lisp — Paradigm(s) Multi paradigm: procedural, functional, object oriented, meta, reflective, generic Appeared in 1984, 1994 for ANSI Common Lisp Developer ANSI X3J13 committee Typing discipline …   Wikipedia

• List of paradoxes — This is a list of paradoxes, grouped thematically. Note that many of the listed paradoxes have a clear resolution see Quine s Classification of Paradoxes.Logical, non mathematical* Paradox of entailment: Inconsistent premises always make an… …   Wikipedia