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Math Help - Continuous Probability Distributions

  1. #1
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    Post Continuous Probability Distributions

    3.27 walpole

    The time to failure in hours of an important piece of electronic equipment used in a manufactured DVD player has the density function

    f(x) = 1/2000 exp (-x/2000), x>=0
    0, x<0

    find F(x).

    my queries :
    - so meaning integrate from 0 to x or 0 to infinity ?
    - and could i use du=-x/2000 dx to solve ? i saw some of my mates using dt. which i don't know how does dt fit in .

    pls advise. thks!
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  2. #2
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    Quote Originally Posted by hazel View Post
    3.27 walpole

    The time to failure in hours of an important piece of electronic equipment used in a manufactured DVD player has the density function

    f(x) = 1/2000 exp (-x/2000), x>=0
    0, x<0

    find F(x).

    my queries :
    - so meaning integrate from 0 to x or 0 to infinity ?
    - and could i use du=-x/2000 dx to solve ? i saw some of my mates using dt. which i don't know how does dt fit in .
    F(x) = \int\limits_0^x {\frac{{\exp ( - t/2000)}}{{2000}}dt}
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  3. #3
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    ok, o to x

    but why do you use t ?
    it doesn't matter if i use u or t (du or dt ) right ?

    and also, if x>0, then it would integrate from 0 to x.
    but since x>= 0, so integrate from 0 to x.
    am i right to conclude this ?
    Last edited by mr fantastic; November 20th 2009 at 08:00 PM. Reason: Merged posts
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  4. #4
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    Quote Originally Posted by hazel View Post
    ok, o to x

    but why do you use t ?
    it doesn't matter if i use u or t (du or dt ) right ?

    and also, if x>0, then it would integrate from 0 to x.
    but since x>= 0, so integrate from 0 to x.
    am i right to conclude this ?
    t is a dummy variable of integration.
    Yes, you integrate from 0 to x.
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  5. #5
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    if x>0, then it would integrate from 0 to infinity ?
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  6. #6
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    Quote Originally Posted by hazel View Post
    if x>0, then it would integrate from 0 to infinity ?
    If you want to get F(x) then I've already said that you integrate from 0 to x.
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