MATH 131 TEST 3 REVIEW SHEET 2021 10. An economist wants to estimate the mean income for the first year of work for college graduates. Determine the minimum required sample size to construct a 95% confidence interval such that the sample mean is within $500 of the population mean. Assume that the population standard deviation is $6250. 11. In a random sample of 17 shoppers at a grocery store express lane, the mean amount spent was $28.13 and the standard deviation was $12.05. Assume the population is normally distributed. a) What distribution should be used to construct a 95% confidence interval for the population mean? Justify your answer. b) Construct a 95% confidence interval from above. I treatment in an emergency room, 80 of the accidents