A Consumer Group Is Performing an Experiment to Evaluate the Tartar-Fightingproperties

A consumer group is performing an experiment to evaluate the tartar-fightingproperties of different brands of toothpaste. Three brands of toothpaste are beingcompared in a randomized comparative experiment. (There is no "do-not-brush"control group.) 300 adult volunteers of varying ages (100 for each toothpaste brand)have been randomly assigned to the treatments. The toothpaste for each brand isdelivered in containers that are the same except for the letters, X, Y, and Zprominently displayed. A team of dentists, blind to the identities of the toothpastebrands, will evaluate the levels of tartar on the subjects' teeth after 2 months of use.The subjects have been instructed to brush their teeth as they normally do during thecourse of the experiment.(a) What is the explanatory variable (factor) for this experiment?
(
b) What is the response variable for this experiment?
(c) After the onset of the experiment, it was discovered that a significant number ofvolunteers using Brand Y toothpaste recently enrolled in a short class on healthpractices, and one of the lessons involved instruction in effective brushing techniques.If none of the volunteers using Brands X and Z enrolled in the class, how would thisaffect the consumer group's interpretation of the results of the experiment?