How many interviews do I need for a qualitative dissertation?
- Expert answer
- Master's
- Asked
The question
I am planning semi-structured interviews for my MSc dissertation. My supervisor said there is no fixed number, but I need to justify my sample size in the methodology chapter and do not know what to cite.
Short answer
There is no fixed number, so justify it through saturation and the scope of your question. Guest, Bunce and Johnson (2006) found most themes emerged within twelve interviews in a fairly homogeneous group, which is a widely cited reference point for a master's project.
Full expert answer
Research methods supervisor
PhD Organisational Behaviour
Your supervisor is right, and the good news is that examiners do not expect a magic number. They expect a reasoned justification that fits your research question, your participants and your analysis method.
Arguments you can make
- Saturation: you stopped when new interviews were no longer producing new codes, and you can show how you tracked that
- Homogeneity: a narrowly defined group, such as HR managers in UK tech SMEs, reaches saturation sooner than a diverse one
- Depth: thematic analysis of long interviews can justify fewer participants than shorter, structured ones
- Precedent: comparable published studies and their sample sizes
What to cite
Guest, Bunce and Johnson (2006) in Field Methods is the usual reference for saturation in interview studies. Braun and Clarke's later work is useful if you use reflexive thematic analysis, because they argue that saturation is not always the right concept for that approach, which shows the examiner you have read critically.
This answer explains a method for you to apply to your own work. Copying it into a submission would count as plagiarism, and it is indexed by similarity checkers.
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