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 lozenge form, or a placebo gum, syrup or lozenge in five doses per day for 3 months. According to a report in the October issue of the Journal of Pediatrics, the incidence of ear infections were reduced by 40% in children given xylitol chewing gum, 30% in those given syrup and 20% in those given lozenges when compared to children give a placebo.
a. Is this an observational study or a randomized experiment?
b. If this is an experiment, what are the three criteria in this case?
c. What are the explanatory and response variables?
d. If it is an experiment, diagram the randomized comparative experiment.