The waiting time in minutes before being served in a local post office is observed for
50 randomly chosen customers:
(a) Test for normality using a = 0.05. What inferences can you draw?
(b) Estimate the mean and standard deviation of the waiting times.
(c) If the goal of the post office is for the waiting time not to exceed 4 minutes, find the capability indices CPU and Cpk and comment on these values. Assuming normality, what proportion of the customers, if any, will have to wait for more than 4 minutes?

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2.1 0.8 4.8 0.5 0.4 2.8 2.5 5.2 3.6 4.2 2.0 9 2.4 2.7 18 2.5 4.6 3.8 5 3.9 3.2 5.5 2.5 3.8 5.0 4.6 2.0 2.1 2.8 16 3.8 4.2 1.5 3.5 5.2 4.8 3.9 2.6 3.5 2.4 3.5