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Posted by MT on Tuesday, July 2, 2013 at 2:59pm.

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?

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

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

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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