Final answer:
The Hawthorne effect refers to changes in behavior that occur when participants are aware they are being observed in a study. It can affect the results of an experiment because participants may behave differently when they know they are being watched.
Step-by-step explanation:
The Hawthorne effect can be defined as results that occur when the behavior of the participants is influenced by the experimenter's knowledge of who is in the control group and who is in the experimental group. It occurs because people change their behavior when they know they are being observed as part of a study. For example, if a researcher tells students they will be observed as part of a study on tutoring effectiveness, the students might not behave naturally.