Thursday, 14 February 2013

Amazing statistical fact #2

In any gathering of people, how many must there be to be 50% sure that at least two people will share the same birthday?

Answer:  At least 27 people.

How many people at that gathering must there be to be virtually certain that two of them will share the same birthday?

Answer:  At least 57 people.

As people enter a room one at a time, which one is most likely to be the first to have the same birthday as someone already in the room?

Answer:  The 20th person to arrive.

What is the average number of people (selected at random) required to find two with the same birthday?

Answer:  On average, 25 people are required.

[Example: There have been 27 Prime Ministers of Australia.   Paul Keating, the 24th Prime Minister, and Edmund Barton, the first Prime Minister, share the same birthday, 18 January.]

Source:  All this and more can be found at:

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