Answer:
Answer is the ethnography
Explanation:
Ethnography can be described as a study of people through the means of interacting with them in their own environment. This might involve the process of joining or living with them in that environment.
This method method is very important especially to researchers. Because it will help the to have the best and rich understanding as to how and the reason why some activities are being carried out by some certain groups of people.
In the case of Leon Festinger and his colleagues, they made use of this method by joining the cult in order to know how and why they create, think and behave in such manners.