(Sp) From a random sample of size 12 from a normal distribution, one has calculated the 95% confidence interval for u and obtained the result (18.6, 26.2). (a) Calculate the sample mean and variance. (b) Calculate the 99% confidence interval for . (c) Without calculating p-value, what are your conclusions for testing the two
hypotheses (i) Ho: u = 20 vs Ha: u # 20, and (ii) Ho: u = 18 vs Ha: u # 18