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Math Help - Probability that 2 out of n have the same Bday

  1. #1
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    Probability that 2 out of n have the same Bday

    Question :
    What is the probability that atleast two out of n persons have the same birthday ? Assume 365 days in a year and all days are equally likely
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  2. #2
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    Quote Originally Posted by zorro View Post
    Question :
    What is the probability that atleast two out of n persons have the same birthday ? Assume 365 days in a year and all days are equally likely
    Pr(at least 2) = 1 - Pr(None) - Pr(1).

    Now read this: Birthday problem - Wikipedia, the free encyclopedia
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  3. #3
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    Still need some clarification

    Quote Originally Posted by mr fantastic View Post
    Pr(at least 2) = 1 - Pr(None) - Pr(1).

    Now read this: Birthday problem - Wikipedia, the free encyclopedia
    In the eq provided

    Pr(at least 2) = 1 - Pr(None) - Pr(1).


    1 - Pr(None) = Pr of all having the same Bday
    Pr(1) = Pr of 1 having the same Bday

    am i correct!!! then how is
    (Pr of all having the same Bday) - (Pr of 1 having the same Bday) = (Pr of atleast 2)


    please explain me i am dum!!!!!
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  4. #4
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    Quote Originally Posted by zorro View Post
    In the eq provided

    Pr(at least 2) = 1 - Pr(None) - Pr(1).


    1 - Pr(None) = Pr of all having the same Bday
    Pr(1) = Pr of 1 having the same Bday

    am i correct!!! then how is
    (Pr of all having the same Bday) - (Pr of 1 having the same Bday) = (Pr of atleast 2)


    please explain me i am dum!!!!!
    At least two means more than one. Think about it.
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  5. #5
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    Thank u Mr fantastic

    Quote Originally Posted by mr fantastic View Post
    At least two means more than one. Think about it.
    Thank u Mr fantastic
    Cheers
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