The manager of a local fast-food restaurant is interested in improving the service provided to customers who use the restaurant’s drive-up window. As a first step in this process, the manager asks his assistant to record the time it takes to serve a large number of customers at the final window in the facility’s drive-up system. The results are in the file P07_08.xlsx, which consists of nearly 1200 service times. For this problem, you can assume that the population is the data in this file.
a. Use Excel to generate a simple random sample of size 30 from the data.
b. Calculate a point estimate of the population mean from the sample selected in part a. What is the sampling error, that is, by how much does the sample mean miss the population mean?
c. Calculate a good approximation for the standard error of the mean.
d. If you wanted to halve the standard error from part c, what approximate sample size would you need? Why is this only approximate?