The emergency department physician of Exercise 4.8 is concerned not only about the average heart rate of the trauma patients but also about the variability. Even if the mean is satisfactory, if the standard deviation is too large, outlying patients would be at risk. Recall that n - 8, m - 67.75 beats/min, and s -- 9.04 beats/min. Establish 95 % confidence intervals on

(a) the variance and

(b) the standard deviation.