An operational statement in psychology is the set of rules by which a researcher will measure behaviors and qualities in an experiment.
For example, let’s say you’re doing a study on participants to find out how much more attractive they can become over the course of 6 months after trying really, really hard at the gym. Like super hard. One way to measure this would be a simple scale of 1-10 from a large group of random participants.
Another way would be to ask my mother, but the answer will always be 11.