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Math Help - Continuous random variables and their probability distributions question

  1. #1
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    Continuous random variables and their probability distributions question

    A probability density function for the lifetime t hours of Electra light globes is given by the rule:
    f(t)=ke^(-t/200), t > 0
    Find:
    a) the value of the constant k
    b) the probability that a bulb will last more than 1000 hours.
    I understand how to complete part b of the question, however I need to answer a beforehand, and I have no idea even where to begin to find the answer.
    Thanks.
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  2. #2
    Grand Panjandrum
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    Re: Continuous random variables and their probability distributions question

    Quote Originally Posted by juliacoolness View Post
    A probability density function for the lifetime t hours of Electra light globes is given by the rule:
    f(t)=ke^(-t/200), t > 0
    Find:
    a) the value of the constant k
    b) the probability that a bulb will last more than 1000 hours.
    I understand how to complete part b of the question, however I need to answer a beforehand, and I have no idea even where to begin to find the answer.
    Thanks.
    To be a density you need:

    \int_0^{\infty}ke^{-t/200}\; dt =1

    This will determine the value of k

    CB
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  3. #3
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    Re: Continuous random variables and their probability distributions question

    Thank you so much. I used that and I got the right answer of k=1/200.
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