One of the major measures of the quality of service provided by a hospital is the speed with which it attends to its emergency room patients. The file ER contains a random sample of waiting times of 70 patients in emergency rooms at various hospitals across Eastern Europe.

a. Construct a 95% confidence interval estimate for the population mean waiting time at the ER.

b. What assumption must you make about the population distribution in order to construct the confidence interval estimate in (a)?

c. Do you think that the assumption needed in order to construct the confidence interval estimate in (a) is valid? Explain.

d. What effect might your conclusion in (c) have on the validity of the results in (a)?