Suppose we want to design a new placebo-controlled trial to evaluate an experimental medication to increase lung capacity. the primary outcome is peak expiratory flow rate, a continuous variable measured in liters per minute. the primary outcome will be measured after 6 months on treatment. the investigators expect to lose 10% of the participants over the course of follow up. the expected peak expiratory flow rate in adults is 300 with standard deviation of 50. how many subjects should be enrolled to ensure 80%power to detect a difference of 15 liters per minute with a two sided test and =0.05?