Based on research from the Nielsen Norman Group, for qualitative research, you need 5 respondents per segment. For instance, if we want to study the experiences of students, retirees, and office workers, we'd conduct 15 interviews. However, depending on the priority of the segment, you can conduct between 2 and 5 interviews. After 5 interviews, we gain less new information relative to the resources invested in terms of time, finances, and human resources.