2. Let's plan a clinical trial to evaluate the efficacy of a new drug designed to reduce SBP (Ex. 9 LS). The plan is to enroll participants and to randomly assign them to receive either the new drug or a placebo. SBP will be measured in each participant after 12 weeks on the assigned treatment. Based on prior experience with similar trials, the investigator expects that 10% of all participants will be lost to follow up or will drop out of the study. If the new drug shows a 5-unit reduction in mean SBP, this would represent a clinically meaningful reduction. How many patients should be enrolled in the trial to ensure that the power of the test is 80% to detect this difference? A two sided test will be used with a 5% level of significance. In order to compute the effect size, an estimate of the variability in SBP is needed. Analysis of data from the Framingham Heart Study showed that the standard deviation of SBP was 19.0. This value can be used as the variability in SBP to plan the trial. A. What is the effect size (see formula for Cohen's D effect size estimate)? Example: d=5/19.0