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Homework Help: Probabilit y of a valve falling in a time period

  1. Nov 15, 2007 #1
    1. The problem statement, all variables and given/known data

    A large population of nominally identical "fail to close" control valves are put into service on the same day on similar installations. The number of valve failures per month N was recorded over time and shown to be given approximately by the following equation

    Calculate the probability that the valve fails in the time period (0,24) months

    2. Relevant equations

    N = 0.001 X t^1.26 (failures/month)

    3. The attempt at a solution

    have tried it with the density function and the cumulative distribution function with N being lambda but still far away from the ans of 0.4414

    The second part of the question also has be stumped as it states if the installation contains 3 valves in unrelated parts of the plant, calculate the probability that the installation is free of valve failure over the same time period (ans is 0.1743)
    Last edited: Nov 16, 2007
  2. jcsd
  3. Nov 15, 2007 #2


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    Science Advisor

    What was the question that 0.4414 is the answer to? I see no question given here!

    What time period?
  4. Nov 16, 2007 #3
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