In-depth interview (IDI) is a cornerstone of qualitative research, and the original classic setting for market research of all types: detailed interviews, usually with one respondent.
This type of interview is ideal for detailed exploration of specific ideas, or evaluation of concepts and materials that require thorough focus and concentration. It can also often be the most appropriate setting for research covering more emotional topics, as the relationship between moderator and respondent is key to the outcomes and insight generated from each interview.
Dyads and triads
Dyads and triads are IDI’s with two or three respondents. This setting allows for maintenance of focus on details, and also incorporates an interactive element which can be very useful when there are polarizing or more controversial elements to explore.