Answer: Naturalistic Observation
Explanation: Professor Carter is using Naturalistic Observation. This is a research method that studies the subjects of a study in their natural environment. It is suitable for studies that do not want to influence the behavior of the subjects, and where the scientist is just a passive onlooker.
Carrying this kind of experiment in a laboratory may change the shopping patterns of the people being studied. Also, it may be unrealistic and expensive to aim to recreate a supermarket in a laboratory
