1 and 2

Complete all questions using the appropriate formulas: 1. A simple random sample of 100 items results in a sample mean of 80. The population standard deviation is ox = 15. a. Construct a 99% confidence interval estimate for the population mean. 2. "Customers arrive at the movie theater at the movie time indicated only to find they need to sit through commercials and previews. Many complain that this time is too long. WSJ 2012 determined in a preliminary sample that the population standard deviation of the amount of time devoted to previews is 4 minutes. If we want to estimate the population mean time for previews at movie theatres with a margin of error of 75 seconds, what sample size should be drawn?" a. Assume a 95% confidence level b. Assume a 99% confidence level