In the paper "A Randomized Trial of Intensive Lipid-Lowering Therapy in Calcific Aortic Stenosis" (New England Journal of Medicine, Vol. 352, No. 23, pp. 2389-2397), S. Cowell et al. reported the results of a doubleblind, placebo controlled trial designed to determine whether intensive lipid-lowering therapy would halt the progression of calcific aortic stenosis or induce its regression. The experiment group, which consisted of 77 patients with calcific aortic stenosis, received 80 mg of atorvastatin daily. The change in their aorticjet velocity over the period of study (one of the measures used in evaluating the results) had a mean increase of 0.199 meters per second per year with a standard deviation of 0.210 meters per second per year.
a. Obtain and interpret a 95% confidence interval for the mean change in aortic-jet velocity of all such patients who receive 80 mg of atorvastatin daily.
b. Can you conclude that, on average, there is an increase in aortic-jet velocity for such patients? Explain your reasoning.