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Probability Question

  1. Feb 20, 2014 #1


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    Staff: Mentor

    An event has an 8% chance to occur per try. How would I calculate the chance of the event occurring at least once after 3 tries?
  2. jcsd
  3. Feb 20, 2014 #2


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    Science Advisor

    Is the probability in one trial independent of the actual results in the others?

    If so, can you write a formula for the event to not occur at all in three tries?
  4. Feb 20, 2014 #3


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    The chance of it not occurring in 3 tries is $$0.92^3$$
    So, you want $$1- 0.92^3$$
  5. Feb 20, 2014 #4


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    Staff: Mentor

    To gain some insight into this problem, try the following brute-force method. List all the possible outcomes for the set of three tries:

    1=no, 2=no, 3=no : probability = 0.92 * 0.92 * 0.92 = …
    1=yes, 2=no, 3=no : probability = 0.08 * 0.92 * 0.92 = …

    Enumerate all the outcomes (how many of them are there?), calculate the probability for each one, and add up the ones that meet your criterion.
  6. Feb 20, 2014 #5


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    Staff: Mentor

    Awesome. Thanks guys.
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