A study was carried out to compare two different methods, injection and nasal spray, for administering flu vaccine to children under the age of 5. All 8000 children in the study were given both an injection and a spray. However, the vaccine given to 4000 of the children actually contained just saltwater, and the spray given to the other 4000 children also contained just saltwater. At the end of the flu season, it was determined that 3.9% of the children who received the real vaccine via nasal spray contracted the flu, whereas 8.6% of the 4000 children receiving the real vaccine via injection contracted the flu.
a. Why do you think each child received both an injection and a spray?
b. Does one method for delivering the vaccine appear to be superior to the other? Test the appropriate hypotheses.
[The study was described in the article "Spray Flu Vaccine May Work Better Than Injections for Tots," San Luis Obispo Tribune, May 2, 2006.]