Health insurers and the federal government are both putting pressure on hospitals to shorten the average length of stay (LOS) of their patients. The average LOS in the United States is 4.6 days (Healthcare Cost and Utilization Project Statistical Brief, December 2018). A random sample of 20 hospitals in one state had a mean LOS of 3.8 days and a standard deviation of 1.2 days.

a. Use a 90% confidence interval to estimate the population mean LOS for the state’s hospitals.

b. Interpret the interval in terms of this application.

c. What is meant by the phrase “90% confidence interval”?