9. Find the critical values I: and IR: that correspond to the given condence level and sample size. (i) 95%; n = 27 1,2 = __________ 3,2: (ii) 99%; n = 41 9,2 = z= (iii) 90%; n = 91 2'12 = IRE: 10. 50 students were polled and asked their age. The sample mean was 23.4 years and the sample standard deviation was 7.2 years. Assume student ages are appr0ximately normally distributed. Find a 90% condence interval estimate for the population standard deviation 0'. Since the mean and standard deviation are given to tenths place, so should the limits of your interval.