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Math Help - Stats Problem

  1. #1
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    Stats Problem

    Hello,

    Could someone please let me know what they got as the answer for this question:


    A company selling vegetable seeds in packets of 40 estimates that the mean number of seeds that will actually grow is 36.0 with a standard deviation of 1.8 seeds. If a customer buys 9 different seed packets, what are the expected value and standard deviation of the number of bad seeds? Assume that packets are independent of each other.



    a. μ = 108.00, σ = 16.2

    b. μ = 324, σ = 5.40

    c. μ = 108.00, σ = 5.40

    d. μ = 324, σ = 145.8

    e. μ = 324, σ = 16.2


    Thank you
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  2. #2
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    Quote Originally Posted by Mike123 View Post
    Hello,

    Could someone please let me know what they got as the answer for this question:


    A company selling vegetable seeds in packets of 40 estimates that the mean number of seeds that will actually grow is 36.0 with a standard deviation of 1.8 seeds. If a customer buys 9 different seed packets, what are the expected value and standard deviation of the number of bad seeds? Assume that packets are independent of each other.

    Mr F says: I don't agree with any of the options given below. If the question was asking for the expected value and standard deviation of the number of good seeds, then one of the options below is correct.

    a. μ = 108.00, σ = 16.2

    b. μ = 324, σ = 5.40

    c. μ = 108.00, σ = 5.40

    d. μ = 324, σ = 145.8

    e. μ = 324, σ = 16.2


    Thank you
    Let X be the random variable number of good seeds in a packet. Then E(X) = 36.0 and var(X) = 1.8^2.

    Let Y be the random variable number of good seeds in 9 packets. Then Y = 9X.

    E(Y) = 9E(X) = ....

    Var(Y) = 9^2 Var(X) => sd(Y) = 9 sd(X) = ....
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