A senior scientist at the EPA (Environmental Protection Agency) wishes to estimate the average daily water consumption of a typical four-person household in the U.S. Staff researchers assembled a random sample of 150 four-person households. The sample mean is 240 gallons per household per day and the sample standard deviation is 50 gallons per household per day.

(a) Construct a 90% confidence interval for the population mean. Round to the nearest gallon.

(b) Construct a 99% confidence interval for the population mean. Round to the nearest gallon.

(c) Explain any differences in your answers in parts (a) and (b). Be specific and use statistical reasoning.

Use minitab or excel