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 = (4000035000)/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 = (4000035000)/5000/sqrt(4)
z = 5000/(5000/2)
z = 2
P(z >2) = 0.0228
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