Question 365228
A normal population has a mean of 56 and a standard deviation of 11. You select a random sample of 9.
Compute the probability the sample mean is: (Round your answers to 4 decimal places.) 
(a) Greater than 58.
t(58) = (58-56)[11/sqrt(9)] = 0.5455
P(x-bar > 58) = P(t > 0.5455 when df=8) = 0.30 
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(b) Less than 55.
t(55) = (55-56)/[11/sqrt(3)] = -0.2727
P(x-bar < 55) = P(t < -0.2727 when df=8) = 0.3960
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(c) Between 55 and 58. 
P(55 < x-bar <58) = P(-0.2727 < t < 0.5455 when df=8) = 0.3039
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Cheers,
Stan H.