A researcher wanted to determine if the reaction time in people differs in their dominant hand versus their nondominant hand. To do this he recruited 15 subjects. Each subject was asked to hold a yardstick etween the index finger and thumb. The subject was asked to open the hand, release the yardstick, and then asked to catch the yardstick between the index finger and thumb. The distance that the yardstick fell served as a measure of reaction time. A coin flip was used to determine whether the subject would use their dominant hand first or the nondominant hand. Results indicated that the reaction time in the dominant hand exceeded that of the nondominant hand. This is an example of: