Non-participant observation is the observation in which a researcher observes his participants for his study with their knowledge. But the researcher will not take an active role in the research. This research has been criticized many times. In observation, people behave differently every time. Data collection will be invalid. Hawthorne effect is the example of non-participant observation.
Thus Joe is going to study how prisoners are behaving in the therapy session and prisoners don't know someone is observing them is the example of the study of non-participant observation.
