HEADERS_END

For a group size of n, the probability that all people have a different

The probability that at least one pair share a birthday = 1 - p

| Number _ of People | Chance of _ no pairs | Chance of _ at least _ one pair |

| 1 | 1 | 0 |

| 2 | 0.997 | 0.003 |

| 3 | 0.992 | 0.008 |

| 4 | 0.984 | 0.016 |

| . |

| 22 | 0.524 | 0.476 |

| 23 | 0.493 | 0.507 |

If there are 23 or more (randomly chosen) people in a group then there is a more than even chance that two will share a birthday.