KERCISES 1. A sample of 49 observations is taken from a normal population with a standard deviation of 10. The sample mean is 55. Determine the 99% confidence interval for the population mean. 2. A sample of 81 observations is taken from a normal population with a standard deviation of 5. The sample mean is 40. Determine the 95% confidence interval for the population mean. 3. A sample of 250 observations is selected from a normal population with a population standard deviation of 25. The sample mean is 20. a. Determine the standard error of the mean. b. Explain why we can use formula (9-1) to determine the 95% confidence interval. c. Determine the 95% confidence interval for the population mean