Number of tries needed for occurrence of a certain event

Discussion in 'Probability' started by Shahin, Jul 5, 2010.

  1. Shahin

    Shahin Guest

    Hello all,

    I was wondering is there any way to determine the number (or
    minimum number) of tries needed for occurrence of a certain event? for
    example, how many times we need to flip a fair coin to get a head?
    what information we may need for this?

    Thank you,
    Shahin
     
    Shahin, Jul 5, 2010
    #1
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  2. Theoretically there is no upper limit on the number of times you may
    need to flip a fair coin to get a head.
     
    Frederick Williams, Jul 5, 2010
    #2
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  3. Shahin

    Ray Koopman Guest

    Look up the "negative binomial distribution".
     
    Ray Koopman, Jul 5, 2010
    #3
  4. Or, more simply, the geometric distribution.
     
    Stephen J. Herschkorn, Jul 5, 2010
    #4
  5. Shahin

    link Guest

    I'm reminded of a question I was asked for a job once. There are 3
    different colored marbles in a bag (unknown, but large amount). How
    many times must you draw until you're guaranteed to have 2 of the
    same color?

    Applying this to your question, it really depends on what kind of
    probability you're talking about. Some situations (such as a flip of a
    coin) have no upper limit. Others (such as the one I just presented)
    do.
     
    link, Aug 9, 2010
    #5
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