Sigmund freud developed his theory of human personality by conducting in-depth interviews over an extended period of time, and sharing his findings about each individual client. this type of research approach is known as a(n)

Case study

Explanation:

Case study: It refers to acquire an in-depth analysis of a phenomenon, person, or group by using a descriptive research approach. A variety of techniques can be used to conduct case studies including direct-observation, personal interviews, and psychometric tests. case study is important to get detailed information about a person.

A case study consists of four forms:

1. Exploratory

2. Illustrative

3. Critical

4. Cumulative.