In-Depth Interview — In-Depth Qualitative Interview

A structured interview follows a fixed set of questions in a fixed order, identical for every participant — essentially an oral survey. A semi-structured interview uses an interview guide with topic areas and suggested questions, but the researcher adapts the order and wording in response to the conversation. An unstructured interview begins with one or two broad opening questions and follows entirely from the participant's responses. Most in-depth qualitative interviews are semi-structured: flexible enough to follow participants' accounts but focused enough to address the research question.

There is no universally correct number. The guiding criterion is theoretical or informational saturation — the point at which new interviews are not introducing new themes or conceptual categories. In practice this commonly occurs between 10 and 30 participants, though highly homogeneous samples may saturate earlier and heterogeneous or maximum-variation samples may require more. Declaring a sample size in advance without a saturation rationale is not considered best practice in qualitative research.

Yes. Telephone and video-mediated interviews (via Zoom, Teams, etc.) are now widely accepted in qualitative research and can reduce geographic and logistic barriers. The trade-off is a partial loss of non-verbal cues available in face-to-face interviews. Researchers should note the mode of data collection in their methods section and consider whether it affected participant disclosure, particularly for sensitive topics.

The choice of analytic method should follow from the research question and theoretical framework. Thematic analysis (Braun & Clarke) is the most widely used general approach and suits a broad range of questions. Interpretive phenomenological analysis is appropriate when the question concerns lived experience and meaning. Grounded theory coding is used when the goal is theory generation about a social process. Narrative analysis is appropriate when the structure and sequence of participants' stories are themselves the analytic focus. The in-depth interview is a data-collection method, not an analytic method, so it must be paired with a specified analytic approach.

No. A focus group brings multiple participants together simultaneously and uses group interaction — agreement, disagreement, storytelling, and co-construction of meaning — as part of the data. An in-depth interview is one-to-one and elicits the individual's perspective without peer influence. Focus groups are more efficient for surfacing shared social norms and collective views; in-depth interviews are preferable for sensitive topics, for capturing individual variation, or when the researcher wants to follow a single person's account in depth without group dynamics shaping responses.