Researchers wanted to evaluate whether a certain herb improved memory in elderly adults as measured by objective tests. To do this, they recruited 90 men and 127 women older than 70 years and in good health. Participants were randomly assigned to receive the herb, 45 mg 3 times a day, or a matching placebo. A measure of memory improvement was determined by a standardized test of learning and memory. What type of experimental design is this?What is the population being designed? What is the response variable in this study?What is the factor? What are the treatments? Which of the following is correct?