Researchers wanted to evaluate whether ginkgo, an over-the-counter herb marketed as enhancing memory, improves memory in elderly adults as measured by objective tests. To do this, they recruited 98 men and 132 women older than 60 years and in good health.
Participants were randomly assigned to receive ginkgo, 40 milligrams (mg) 3 times per day, or a matching placebo. The measure of memory improvement was determined by a standardized test of learning and memory. After 6 weeks of treatment, the data indicated that ginkgo did not increase performance on standard tests of learning, memory, attention, and concentration. These data suggest that, when taken following the manufacturer’s instructions, ginkgo provides no measurable increase in memory or related cognitive function to adults with healthy cognitive function.
(a) What type of experimental design is this?
(b) What is the population being studied?
(c) What is the response variable in this study?
(d) What is the factor that is set to predetermined levels? What are the treatments?
(e) Identify the experimental units.
(f ) What is the control group in this study?
(g) Draw a diagram similar to Figure 7 or 8 to illustrate the design.