Echinacea is an herbal supplement that is often used an over…
Echinacea is an herbal supplement that is often used an over-the-counter cold remedy. A team of scientists decided to investigate its effectiveness. They hypothesized that echinacea reduces the effect of the common cold on the body because it boosts the ability of the immune system to fight off the virus. The images below report the experimental design and the results. Based on this information, choose the best conclusion for the study from the provided options.