Researchers at the University of Washington conducted an experiment to determine whether the herbal remedy Echinacea is effective in treating children’s colds and other respiratory infection (National Post, December 3, 2003). A sample of 524 childrens was recruited. Half the sample treated their colds with Echinacea, and the other half was given a placebo. For each infection, the duration of the colds (in days) was measured and recorded. Can we conclude that Echinacea is effective?