Can a study have ONE research participant? Sampling in qualitative research

A qualitative study can include just one research participant, but defending that choice requires more than convenience. The case for a single-participant design hinges on three things: the philosophical stance behind the research, the specific purpose of the study, and the richness of the data collected. When those elements align, one participant can produce findings that are detailed enough to stand on their own—especially in approaches aimed at deep, subjective understanding rather than broad claims.

The first justification rests on worldview. Qualitative research is often conducted under non-positivist assumptions (commonly interpretivist rather than positivist), where the goal is not to discover universal truths or generalize to a population. If the study is designed to explore an individual’s unique experiences or worldview, then criticisms about “too small a sample” miss the point: generalizability is not the target. In that framing, a one-person sample can be treated as a legitimate unit of analysis rather than a statistical limitation.

Even so, one participant is still an extreme choice, so the argument needs a second pillar: the usable quality of the data. Sample size in qualitative work is not determined by a fixed number; it depends on how much meaningful material the study generates. The transcript contrasts studies with five or ten participants that produced enough depth to reach saturation and develop themes, with studies that recruited 20 or 30 participants but collected short interviews or incomplete data, resulting in less usable material. A key idea is an inverse relationship: more usable data per participant can reduce the need for more participants.

The third pillar is what the research intends to do with that data. An example cited from Jones and L. describes a study focused on one person’s views on perceived life skills development. Although there was only one participant, the researchers conducted five interviews, accumulating about 30 hours of data. The defense emphasized that the aim was not to generate universal patterns, but to explore lived experience in depth.

That “lived experience” framing connects naturally to phenomenology. The transcript notes that phenomenological research typically examines lived experiences of a small group, but it can also be pushed further using a single case. It specifically references interpretive phenomenological analysis (IPA) and quotes IPA’s originator on the possibility of conducting IPA on a single case, arguing that such work can be important and that PhD students should consider bold, detailed analyses of one person.

Finally, the transcript offers a practical decision rule: one participant may fit when the study targets highly personal phenomena (such as coping with trauma) and can sustain depth through extensive interviewing. By contrast, topics like students’ views on a teaching approach may more naturally call for multiple participants to capture variation. The overall takeaway is that sample size is a defensible methodological choice when worldview, purpose, and data quality all support it.