Customers arrive at a movie theater at the advertised movie time only to find that they have to sit throogh several previews and prepreview ads before the move starts. Many complain that the time devoted to previews is too long. A preliminary sample conducted by the iwall stroet fournal thowed that the standard deviation of the ameunt of fimen devoted to previews was 4 minutes. Use that as a planning value for the standard deviation in answering the following questions. Round your answer to next whole number a. If we want to estimate the population mean time for previews at movie theaters with a margin of error of 75 seconds, what sample size should be used? Assume 95% confidence. b. If we want to estimate the population mean time for previews at movie theaters with a margin of error of 1 minute, what sample ste should be usedr Asoume 95% confldence. Customers arrive at a movie theater at the advertised movie time only to find that they have to sit throogh several previews and prepreview ads before the move starts. Many complain that the time devoted to previews is too long. A preliminary sample conducted by the iwall stroet fournal thowed that the standard deviation of the ameunt of fimen devoted to previews was 4 minutes. Use that as a planning value for the standard deviation in answering the following questions. Round your answer to next whole number a. If we want to estimate the population mean time for previews at movie theaters with a margin of error of 75 seconds, what sample size should be used? Assume 95% confidence. b. If we want to estimate the population mean time for previews at movie theaters with a margin of error of 1 minute, what sample ste should be usedr Asoume 95% confldence