statistics

Given the information on the sample below, use the steps to construct a 95% confidence interval for the population mean. Assume that the population is normally distributed. A college gives the same calculus final to all sections of the course. A sample of thirty randomly selected students that took the calculus final was collected after the exam. The mean score of the sample was 80 and the standard deviation of the sample was 13.2. a) Find the critical value to that corresponds to a 95% confidence level. b) Calculate "E" c) Construct your confidence interval. d) Write a sentence that explains the meaning of the confidence interval. I am 95% confident that.. The mean replacement time for a random sample of 20 washing machines in 7.2 years and the standard deviation is 3.1 years. Construct a 95% confidence interval for the population standard deviation of the replacement times of a washing machines of this type. a) Find the two critical values xz and x; that correspond to a 95% confidence interval. b) Construct your confidence interval. c) Write a sentence that explains the meaning of the confidence interval