Purposive sampling deliberately selects participants or cases for their relevance to a research question. The aim is to obtain useful perspectives or experience, rather than to give every population member a known probability of selection. Explain the selection logic and how it supports your analysis.
Start with a question, not a preferred participant
Consider an original planning scenario: “How do first-generation students experience their first dissertation-supervisor meeting?†You need participants who have had that experience. Interviewing anyone available in the cafeteria would not necessarily answer the question, even if recruiting them were easier.
Define “first-generation†consistently for your project and make participation voluntary. Avoid collecting unnecessary family details. Specify how recently the meeting must have occurred so participants can discuss it meaningfully. Agree the criteria and consent procedure with your supervisor before recruiting.
Example recruitment matrix
| Decision | Example rationale | Record in your methods |
|---|---|---|
| Include students after their first meeting | They can describe the event being studied. | Eligibility definition and screening question |
| Seek more than one subject area | Supervision arrangements may differ. | Departments reached and any gaps |
| Seek commuters and campus residents | Access and preparation may differ. | Why this variation matters to the question |
| Invite through approved channels | Reduce pressure to take part. | Who issued invitations and how consent worked |
This matrix is illustrative. It does not prescribe a universal quota or sample size. Add only dimensions that matter to the research question, and avoid making the design so complicated that you cannot analyse the resulting variation.
Different selection strategies
A relatively homogeneous group can help explore a shared experience in detail. Seeking contrasting cases can help investigate variation. Selecting people because they meet an explicit experience criterion can keep interviews focused. Whichever strategy you use, explain what counts as a relevant case and why.
The NHS England qualitative-research guide discusses purposive selection in relation to relevant experiences and perspectives. It is a useful introduction, not a substitute for the methodology required by your programme.
Methods paragraph: a model to adapt
The study used purposive recruitment to seek students who had recently attended their first dissertation-supervisor meeting. Selection aimed to include perspectives from more than one subject area and living arrangement because these contexts could shape preparation and access. Recruitment channels and unfilled categories are reported below. The sample was designed for detailed accounts of this experience, not statistical representation of all students.
Replace the general wording with your actual definition, dates, recruitment route, final sample and rationale. Do not claim that you reached saturation merely because recruitment stopped. Explain how adequacy was assessed under the analytic approach you actually used.
Common mistakes
- Choosing only people likely to confirm your argument.
- Calling a friends-only sample purposive without explaining the relevant experience.
- Claiming population percentages from a small interview sample.
- Changing criteria without documenting why.
- Reporting planned variation while hiding gaps in the achieved sample.
Related: convenience sampling, convenience versus purposive sampling, and planning a semi-structured interview.