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?

- Stats -
**Kuai **, Tuesday, July 2, 2013 at 3:11pm
mean = 35000

St.dev =5000

x = 40000

z = (x - mean)/sd/sqrt(n)

- Stats -
**Kuai **, Tuesday, July 2, 2013 at 3:23pm
n =

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

z = 5000/(5000/2)

z = 2

P(z >2)

- Stats -
**Kuai **, Tuesday, July 2, 2013 at 3:28pm
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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