Researchers wanted to evaluate whether ginkgo, an over-the-counter herb marketed as enhancing memory, i K recruited 98 men and 134 women older than 65 years and in good health. Participants were randomly assign measure of memory improvement was determined by a standardized test of learning and memory. After 6 we standard tests of learning, memory, attention, and concentration. These data suggest that, when taken follow or related cognitive function to adults with healthy cognitive function.
(a) What type of experimental design is this?
A. Cohort study
B. Case-control study
C. Randomized block design
D. Matched-pairs design
E. Completely randomized design