Purposeful sampling allows you to deliberately select individuals and research settings that can help you get the information needed to answer your research questions.
(Ravitch and Carl, 2019, p.128)

In qualitative research, purposeful sampling (also known as ‘purposive’ or ‘selective’ sampling) is one popular method of selecting a subgroup of people from a wider population to include them in a study. When creating a purposeful sample, researchers rely on their own judgement to pre-define which types of participants can provide valuable views for the research objective.

Cartoon robotic hand selecting and inspecting a person from a group.

Image Source: (ThoughtCo, 2020)

Typical characteristics researchers will be looking for in potential members of a purposeful sample are knowledge and experience of a particular issue or context. For example, you might be interested in studying the role of mental health services in combatting bullying in schools. A purposeful sampling strategy could lead you to the following people to include in your study:

  • teachers who know about bullying in schools
  • therapists and social workers providing mental health services in schools
  • students who have experience of accessing mental health services for bullying

There are also practical reasons to select some participants rather than others, for instance:

  • willingness to participate in the study
  • ability to communicate thoughts and feelings in a way that will be useful to the aims of the study
  • providing unusual perspectives on a particular phenomenon or context
  • selecting for maximum variation within a sample
  • finding as homogenous a selection as possible

You can use this five-step process to find a purposeful sample:

  1. decide who you want to study (e.g., young people, health service users, disaster survivors, etc.)
  2. identify purposeful sampling criteria (i.e., decide who should be included in your study)
  3. create a recruitment plan (i.e., outline how you will enrol potential participants in your study)
  4. determine best possible sample size
  5. select and invite participants to your study

(Based on Daniel, 2011)

(Author: Jonathan (Jonny) Adams)

What is it?

Videos:

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Purposive sampling by ACAPS Project (2012)

This video explains how purposeful sampling is different from convenience sampling and describes, with diagrams, some possible approaches to gaining a good purposeful sample.

(Academic reference: ACAPS Project (2012, January 12). Purposive Sampling. [Video]. YouTube. https://www.youtube.com/watch?v=FuzE3Lrw2t0)

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Purposeful sampling by Sarah Shuster (2018)  

This video is a short introduction that explains purposeful sampling in qualitative research. The video outlines different types of purposeful sampling and offers a summary of the strengths and weaknesses of the sampling technique. 

(Academic reference: Shuster, S. (2018, January 28). Purposive sampling [Video]. YouTube. https://www.youtube.com/watch?v=Ag8xsWgyF-0)   

Articles:

Purposeful sampling for qualitative data collection and analysis in mixed method implementation research by Lawrence A. Palinkas et al. (2015)

This article explores how and why you might use purposeful sampling when researching the implementation of complex treatments, interventions or programs and provides a useful summary of the various kinds of purposeful sampling strategies.

(Academic reference: Palinkas, L.A., Horwitz, S.M., Green, C.A., Wisdom, J.P., Duan, N. & Hoagwood, K. (2015). Purposeful sampling for qualitative data collection and analysis in mixed method implementation research. Administration and Policy in Mental Health and Mental Health Services Research, 42(5), pp 533–544. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4012002/)

How is it done?

Videos:

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Sampling methods 101: Probability and non-probability sampling explained simply by GradCoach (2023) 

This 20-minute video introduces the concept of sampling, explaining key terms such as sample and population. It also outlines the different types of probability and non-probability sampling, offering a description and example for each method. The video advises how to select the right sampling method and emphasises the influence of the study aims and available resources when choosing a sampling method.   

(Academic reference: GradCoach. (2023, February 24). Sampling methods 101: Probability and non-probability sampling explained simply [Video]. YouTube. Sampling Methods 101: Probability & Non-Probability Sampling Explained Simply)  

Books:

Qualitative evaluation and research methods by Michael Quinn Patton (1990)

This section of Patton’s book explains several different strategies for selecting a purposeful sample, using examples from the evaluation of different programs, and demonstrates how your required sample size depends on the nature and aims of your study.

(Academic reference: Patton, Q. (1990). Qualitative evaluation and research methods. In designing qualitative studies (2nd ed., pp. 169-186). Sage Publications. https://legacy.oise.utoronto.ca/research/field-centres/ross/ctl1014/Patton1990.pdf)