Sample size in qualitative research
Based on Qualitative Researcher Dr Kriukow's video on YouTube. If you like this content, support the original creators by watching, liking and subscribing to their content.
Use saturation as the practical benchmark for deciding when enough qualitative participants have been recruited.
Briefing
Qualitative research often demands a pre-specified participant count, yet there’s rarely a clear rule for what “enough” looks like. A practical solution is to justify sample size through the concept of saturation—the moment when additional interviews no longer generate genuinely new themes, concepts, or insights, but instead reinforce what’s already emerging in the analysis. In that situation, recruiting more participants adds little value because the thematic framework has effectively stabilized.
Saturation has also faced criticism. Because qualitative data analysis is dynamic and subjective, some researchers argue there’s no single, universally defensible point where data can be declared “exhausted.” New readings can always surface something different, especially when researchers are actively searching for meaning. Still, even with that caveat, experienced qualitative analysts often recognize a practical threshold: later interviews tend to confirm prior patterns rather than overturn them or shift the overall interpretation.
When saturation is expected to arrive depends on multiple study choices, including the methodology, the data-analysis approach, and how deep and detailed the interviews are. In the account here, a typical experience-based window is that saturation often feels reachable between the fifth and the 10th interview. At that stage, new transcripts usually support the existing thematic structure rather than contradict it or introduce a fundamentally new perspective.
The challenge then becomes how to use saturation to decide participant numbers when saturation can only be assessed after recruitment and analysis. The suggested workaround is to anchor the initial sample-size decision in prior empirical research that has examined saturation directly. Studies reviewing hundreds of qualitative projects have reported that saturation commonly occurs with roughly 20 to 50 participants overall. Methodology-specific guidance is also offered: grounded theory studies, for instance, are often associated with saturation around 20 participants.
For a research proposal or funding application, this creates a defensible justification strategy. A researcher can cite the literature on saturation to propose an initial recruitment target—such as 20 participants—while explicitly stating openness to recruiting more if saturation isn’t reached in the actual study. That combination—evidence-based planning plus a contingency plan—helps align the proposal with qualitative realities and reduces the risk of criticism for relying solely on personal judgment.
Cornell Notes
Qualitative studies can’t always specify participant numbers with certainty, so saturation is used as the organizing principle. Saturation is reached when additional interviews stop producing new themes or concepts and instead reinforce the existing thematic framework. Critics note that qualitative analysis is subjective and that “exhaustion” can’t be perfectly defined, but analysts still recognize a practical point where new data adds little value. The timing of saturation varies by methodology, analysis approach, and interview depth; one common experience-based range is between the 5th and 10th interviews. To justify sample size before data collection, researchers can rely on prior studies that have examined saturation, often reporting about 20–50 participants overall and around 20 for grounded theory, while remaining willing to recruit more if saturation isn’t achieved.
What does “saturation” mean in qualitative research, and why does it matter for sample size?
Why do some researchers criticize saturation, and how is that criticism addressed?
What factors influence when saturation is likely to occur?
How can saturation guide participant numbers if saturation can only be judged after recruitment and analysis?
What sample-size ranges are commonly reported for reaching saturation?
What is a defensible strategy for writing a qualitative research proposal about sample size?
Review Questions
- How would you distinguish between data that “supports” existing themes and data that truly changes the thematic framework in a saturation argument?
- What study design elements (methodology, analysis approach, interview depth) could shift the expected point of saturation, and how would you reflect that in your proposal?
- Why is it reasonable to cite prior saturation research when you can’t know saturation in advance, and what contingency plan should accompany that citation?
Key Points
- 1
Use saturation as the practical benchmark for deciding when enough qualitative participants have been recruited.
- 2
Define saturation as the point where new interviews stop producing genuinely new themes and instead reinforce the existing thematic framework.
- 3
Acknowledge that saturation is debated because qualitative analysis is subjective, but rely on a practical threshold where additional data adds limited value.
- 4
Expect saturation timing to vary with methodology, analysis approach, and interview depth; a common experience-based window is between the 5th and 10th interviews.
- 5
Justify pre-study sample size by citing prior empirical research on saturation rather than relying only on personal judgment.
- 6
Plan for flexibility: recruit an initial target based on the literature, but continue sampling if saturation isn’t reached in the study.
- 7
Use methodology-specific saturation expectations when available (e.g., grounded theory often reported around 20 participants).