Comparing corn varieties. New varieties of corn with altered amino acid content may have higher nutritional value than standard corn, which is low in the amino acid lysine. An experiment compares two new varieties, called opaque-2 and floury-2, with normal corn. The researchers mix corn-soybean meal diets using each type of corn at each of three protein levels: 12% protein, 16% protein, and 20% protein. They feed each diet to 10 one-day-old male chicks and record their weight gains after 21 days. The weight gain of the chicks is a measure of the nutritional value of their diet.

(a) What are the individuals and the response variable in this experiment?

118 CHAPTER 6 Experiments in the Real World

(b) How many explanatory variables are there? How many treatments? Use a diagram like Figure 6.1 to describe the treatments. How many experimental individuals does the experiment require?

(c) Use a diagram to describe a completely randomized design for this experiment.

(Don’t actually do the randomization.)

AppendixLO1