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Probability question help?

The weekly repair cost Y for a machine has a probability density function given by f(y) = 3(1-y)^2 for 0<y<1, and 0 elsewhere.

with measurements in hundreds of dollars. how much money should be budgeted each week so that the actual repair cost will exceed the budgeted amount only 10% of the time.

I know I need to integrate, but I simply am not sure on the interval I need to integrate over.

Help?

3 Answers

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  • Anonymous
    10 years ago

    You want to integrate the density function from x to 1 and set it equal to .1

    Then solve for x, and x times 100 is your answer

  • cidyah
    Lv 7
    10 years ago

    Find k such that Integral (k, 1) 3(1-y)^2 dy = .10

    ∫ 3(1-y)^2 dy = -3(1-y)^3 /3 = -(1-y)^3

    Let F(y) =-(1-y)^3

    Integrating from k to 1

    F(1) =0

    F(k) = -(1-k)^3

    F(1)-F(k) = 0 - (-(1-k)^3) = .10

    (1-k)^3 = .10

    3 log(1-k) = log(.10)

    log(1-k)=log(0.10)/3

    1-k = e^log(0.10)/3

    k = 1-e^[log(0.10)/3]

    k=0.5358 (in hundreds of dollars)

  • Anonymous
    10 years ago

    You're probably not going to get the correct answer here.

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