Can low-fat food labels lead to obesity? What are the effects of low-fat food labels on food consumption? Do people eat more of a snack food when the food is labeled as low-fat? The answer may depend both on whether the snack food is labeled low-fat and whether the label includes serving-size information. An experiment investigated this question using university staff, graduate students, and undergraduate students at a large university as subjects. Subjects were asked to evaluate a pilot episode for an upcoming TV show in a theater on campus and were given a cold 24-ounce bottle of water and a bag of granola from a respected campus restaurant called The Spice Box. They were told to enjoy as much or as little of the granola as they wanted. Depending on the condition randomly assigned to the subjects, the granola was labeled as either "Regular Rocky Mountain Granola" or "Low-Fat Rocky Mountain Granola." Below this, the label indicated "Contains 1 Serving," or "Contains 2 Servings," or it provided no serving-size information.21 Twenty subjects are assigned to each treatment, and their granola bags were weighed at the end of the session to determine how much granola was eaten.

(a) What are the factors and the treatments? How many subjects does the experiment require?

(b) Outline a completely randomized design for this experiment. (You need not actually do the randomization.)