Echinacea is widely used as an herbal remedy for common cold, but does it work? In a double-blind experiment, healthy volunteers agreed to be exposed to common-cold- causing rhinovirus type 39 and have their symptoms monitored. The volunteers were randomly assigned to take either a placebo of an Echinacea supplement for 5 days following viral exposure. Among the 103 subjects taking a placebo, 88 developed a cold, whereas 44 of 48 subjects taking Echinacea developed a cold. (use plus 4 method) Give a 95% confidence interval for the difference in proportion of individuals developing a cold after viral exposure between the Echinacea and the placebo. State your conclusion.
