Suppose that 9 observations are selected at random from the normal distribution with unknown mean [.t and unknown variance 02. For these 9 observations, Xn = 22 and Z?=1(Xi 02 = 72. (a) Apply a suitable hypothesis test and perform the following hypotheses at the signicance level of 0.05. Comment on the result of hypothesis test if we should accept or reject the null hypothesis. H0: ,u S 20 H1: [1 > 20 (10 marks) (b) Construct the condence interval for [.l with the condence level of 0.95. f l 0 marks\\