An orderly and scientific study of a subgroup by a researcher after having been accepted as a member is called:

The answer is participant observer. A participant observer is classified as a method in which is used in collecting data for research. It is a method where a person joins a particular group in order to know or learn more about them in a way that they could join them or before the person could be accepted. The person usually records and observe as he or she joins the group to know more about the group that he or she is getting into.