SOLUTION: In a group of 8 people, what is the probability that at least 2 persons have the same birthday. (the same month and day, excluding February 29)

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Question 1129119: In a group of 8 people, what is the probability that at least 2 persons have the same birthday. (the same month and day, excluding February 29)
Answer by ikleyn(52780) About Me  (Show Source):
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The complement event is that in a group of 8 people all have different birthdays,

and the probability of this complement event is 


    P' = %28364%2F365%29%2A%28363%2F365%29%2A%28362%2F365%29%2Aellipsis%2A%28358%2F365%29 = %28%28365-1%29%2A%28365-2%29%2A%28365-3%29%2Aellipsis%2A%28365-7%29%29%2F365%5E7 = 0.925665 (approximately).


Then the probability of the event under the question is the complement to it


    P = 1 - P' = 1 - 0.925665 = 0.074335 = 7.4335%.       ANSWER

Solved.