Final answer:
An operational definition in a controlled experiment is crucial for ensuring that variables are measured in a consistent and valid manner, and it specifies how a variable will be measured.
Step-by-step explanation:
An operational definition in a controlled experiment specifies how a variable will be measured. For example, if we are studying the effect of a tutoring program on student grades, the operational definition would clarify what constitutes a "good" grade and precisely describe what "tutoring" entails.
This definition ensures that the variables are measured in a consistent, reliable, and replicable manner, which is crucial for the validity of the experiment's findings. Moreover, it allows other researchers to understand exactly how and what is being measured, which is essential for interpreting data and potentially repeating the experiment to verify the results.