Students completing a project for their statistics class were testing whether, when blindfolded, subjects would be more likely to identify the flavor of an orange Starburst or a lemon Starburst. The subjects were only told that they would taste two flavors of Starburst. The researchers gave all the subjects the orange Starburst first, let them have a drink of water, and then gave them the lemon Starburst. After each Starburst, the subjects were asked what they thought the flavor was. What fundamental component is missing in this experimental design and why is it important?