A news article by Reuters on October 6, 1998, reported:
In a new study, Dr. Matti Uhari and colleagues at the University of Oulu in Finland randomly gave 857 healthy children in daycare centers xylitol in syrup, gum, or a lozenge form, or a placebo gum or syrup in five doses per day for 3 months. According to a report in the October issue of the journal Pediatrics [Vol. 102, pp. 879-884, 971-972, 974-975], the incidence of ear infections was reduced by 40% in children given xylitol chewing gum, 30% in those given syrup and 20% in those given lozenges when compared to children given a placebo.
a. Is this an observational study or a randomized experiment? Explain.
b. What are the explanatory and response variables?
c. Are confounding variables likely to be a problem in this study? Explain.