# Birthday Paradox Probability Estimates

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This Demonstration of the birthday problem shows the probability that at least two individuals share the same birthday assuming that there are 365 equally likely possible birthdays.

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Contributed by: Scott R. Colwell (August 2011)

Open content licensed under CC BY-NC-SA

## Details

The formula for the probability of some people out of to share the same birthday is:

, where is a binomial coefficient.

Reference

[1] E. H. McKinney, "Generalized Birthday Problem," *The American Mathematical Monthly*, 73(4), 1966 pp. 385–387.

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