Matrix
Interview sample size matrix
How population tightness and research depth set your interview count
A two-by-two matrix for scoping a qualitative study. One axis is how tightly the participant population is defined, the other is how broad the research question is. Each quadrant gives a starting range of interviews, from 5 to 8 for a tight audience and a narrow question to 25 to 40 for a diverse audience and a broad one. Start at the lower end and stop when new themes dry up.
Where this appears
What's in this matrix
Vertical axis: Population (Diverse to Tight). Horizontal axis: Research depth (Narrow to Broad).
- Tight and narrow (Tight population, Narrow research depth): 5 to 8 interviews. A focused question for similar participants.
- Tight and broad (Tight population, Broad research depth): 12 to 18 interviews. Deep exploration of one defined audience.
- Diverse and narrow (Diverse population, Narrow research depth): 15 to 20 interviews. Many kinds of people, one focused question.
- Diverse and broad (Diverse population, Broad research depth): 25 to 40 interviews. Plan for several segments and iteration.
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<a href="https://www.koji.so/visuals/interview-sample-size-population-depth-matrix"><img src="https://www.koji.so/visuals/interview-sample-size-population-depth-matrix/interview-sample-size-population-depth-matrix.png" alt="Two-by-two matrix of interview sample size: tight or diverse population against narrow or broad research depth, from 5 to 8 up to 25 to 40 interviews." width="1200" height="630" /></a>
<p>Source: <a href="https://www.koji.so/visuals/interview-sample-size-population-depth-matrix">Interview sample size matrix</a>, Koji</p>
