Question: (4 points) A local shipping company is interested in installing an expensive color copier at one of its offices. As an important part of the decision process, the company’s manager wants to estimate the average number of documents that would be copied daily if the machine were installed. From experience at several other offices, the company’s operational manager believes the standard deviation of the number of documents copied daily is 38. In addition, the number of documents copied daily is a normally distributed random variable. The average number of copies for a selected copy machine over a random sample of 21 days was 368 copies.

a. Find 90% and 95% confidence intervals for the mean.

b. Interpret your answers.

c. What would be the 95% confidence interval for the mean if we increase the number of randomly selected days to 50 days?