Chapter 10, Problem 28SE

Antibiotic or Placebo A large number of surgery patients get infections after surgery, which can sometimes be quite serious. Researchers randomly assigned some surgery patients to receive a simple antibiotic ointment after surgery, others to receive a placebo, and others to receive just cleansing with soap. If we wanted to test the association between treatment and whether patients get an infection after surgery, would this be a test of homogeneity or of independence? Explain. (Source: Hospitals Could Stop Infections by Tackling Bacteria Patients Bring In, Study Finds, New York Times, January 6, 2010.)