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, Jul 5, 2010
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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
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  3. Shahin

    Ray Koopman Guest

    Look up the "negative binomial distribution".
    Ray Koopman, Jul 5, 2010
  4. Or, more simply, the geometric distribution.
    Stephen J. Herschkorn, Jul 5, 2010
  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)
    link, Aug 9, 2010
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