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The incomes in a certain lg. population of college teachers have a normal distribution with a mean of $35,000 and st. dev. of $5000. Four teachers are randomly selected. What is the probability their average salary will exceed $40,000?

  • Stats -

    mean = 35000
    St.dev =5000
    x = 40000
    z = (x - mean)/sd/sqrt(n)

  • Stats -

    n =

    z = (40000-35000)/5000/sqrt(4)
    z = 5000/(5000/2)
    z = 2

    P(z >2)

  • Stats -

    mean = 35000
    st.dev = 5000
    x = 40000

    n = 4

    z = (40000-35000)/5000/sqrt(4)

    z = 5000/(5000/2)
    z = 2

    P(z >2) = 0.0228

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