Suppose the average client charge per hour for out-ofcourt work bylawyers in the

Question

Suppose the average client charge per hour for out-ofcourt work bylawyers in the state of Iowa is $125. Suppose further that a randomtelephone sample of 32 lawyers in Iowa is taken and that the sampleaverage charge per hour for out-of-court work is $110. If thepopulation variance is $525.
(A) what is the probability of getting a sample mean of $110 orlarger?
(B) What is the probability of getting a sample mean larger than$135 per hour?
(C) What is the probability of getting a sample mean of between$120 and $130 per hour?

Explanation / Answer

Given =125, n=32, xbar=110, ^2=525 (a) P(xbar >= 110) = P((xbar-)/(^2/n) >=(110-125)/(sqrt(525/32))) =P(Z>= -3.7) =0.9999 (check normal table) (b) P(xbar > 135) =P(Z> (135-125)/(sqrt(525/32))) =P(Z>2.47) = 0.0068 (check normal table) (c) P(120

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