8.1 Minimum Sample Size for Mean p with o Known (Z- table) You want to obtain a sample to estimate a population mean. Based on previous evidence, you believe the population standard deviation is approximately o = 73.8 . You would like to be 80% confident that your estimate is within 1.5 of the true population mean. How large of a sample size is required? 3976 X8.2 Margin of Error for Mean u with o Unknown (t-table) If n = 16, = 33, and s = 9, find the margin of error at a 98% confidence level Round to 2 decimal places. E = 5.9 X