In-Depth Interviews


What is an In-Depth Interview (“IDI”)?

An in-depth interview is a qualitative research method in which just one person is interviewed, usually for 1.5 up to 2 hours.

Also known as a ‘one-on-one’, there are instances when a third individual may be present, such as a client’s technical expert, engineer, or product development person who can probe and/or clarify questions about specific subject matter.

How is an In-Depth Interview conducted?

IDIs are normally carried out face to face, but occasionally can be done over the phone.A mix can be accomplished with the use of web cams, FaceTime, Skype or similar videoconferencing tools when both parties have them available.

A discussion guide is used to frame the conversation. Many questions are open-ended rather than yes/no or multiple choice format. Because an IDI can veer off in many directions, it is important to leave adequate time for tangential paths to be explored.

When to use IDIs

There are situations where a personal interview is the best, and sometimes the only method that makes sense for eliciting information from a respondent.

  • Doctors, dentists and nurses for instance may be asked about very sensitive topics that they would prefer not to discuss in a group setting.A trained researcher may be able to conduct an interview over the phone if the workplace or an offsite meeting room is not available for such a discussion.
  • Like health, a person’s financial or sexual activity may differ from or be more complex than one’s peers. Despite a reluctance to discuss such private matters in front of a group of strangers, a subject generally feels more relaxed and open in a conversation with just one other person as exists in an in-depth interview.
  • Technology users have unique experiences with their devices that can best be captured, discussed, reported and recorded during a one-on-one interview. Questions about usability, intuitiveness, discoverability and meeting of expectations can all be explored, e.g. while a subject is searching for content on a website, playing a video game, using an app, or multitasking on a smart phone.
  • If the desire is to ensure that feedback is obtained from every respondent, an IDI eliminates the role of a dominant, leading personality that may occur in a focus group.
  • IDIs may be especially helpful in B2B research where subjects are sought who possess unique job skills and knowledge.
  • One helpful feature of an in-person interview is that body language, facial expressions, moods and other non-verbal behaviors can be directly observed, e.g., does a topic make someone smile/laugh, or feel uncomfortable? Such cues provide added information that can be integrated with what a person says they feel about a product, concept, or message.

Costs and other tradeoffs

  • Interviewing one person at a time is one of the most expensive forms of qualitative research. The key value is that a very detailed understanding about an issue, product or service can be obtained. A small group of IDIs can provide the majority of content to pursue in focus groups, or surveys administered to a larger, more projectable sample of a population.
  • While a focus group moderator can gain input from 10 people in the same amount of time required for one in-depth interview, that method involves the costs of facility rental and refreshments, plus the expense of having clients commute to,and spend time viewing the discussion. Also, compared to a 90 minute in-depth interview, a focus group member generally participates (speaks) for at most about one-tenth of the session, or fewer than 10 minutes.
  • Compensation for participating in either an IDI or focus group tends to be about the same amount.  It will vary depending upon the profession and other demographics that impact the difficulty of finding qualified and willing recruits.
  • Less time is needed to schedule an IDI with one person than trying to assemble several people for a focus group.

Final comment. In-depth interviewing is an extremely useful research method, but because of its limited number of subjects (usually 10-25), results should not be used to project to a broad audience. Rather, they should be complemented by, and form the basis of questions for focus groups and larger scale surveys.