Purposive sampling, or judgmental or selective sampling, is a non-probability sampling method where researchers intentionally select participants based on specific criteria or characteristics relevant to the research objectives. Unlike probability sampling methods that rely on random selection, purposive sampling involves the researcher’s judgment and discretion in choosing participants with the desired qualities or characteristics.
Types of purposive sampling include:
- Maximum variation sampling: Selecting participants who represent a broad range of variation in the characteristics of interest, providing a comprehensive perspective.
- Homogeneous sampling: Choosing participants with similar characteristics can enhance understanding within a specific subgroup.
- Typical case sampling: Selecting participants considered typical or representative of the larger population regarding the characteristics being studied.
- Expert sampling: Choosing experts or highly knowledgeable individuals in the subject matter under investigation.
- Criterion sampling: Selecting participants based on specific criteria or qualities relevant to the research objectives.
Some advantages of purposive sampling are:
- Relevance: Purposive sampling ensures that participants are selected based on specific criteria, making their insights directly relevant to the research question.
- Efficiency: It is efficient when researchers seek participants with specific characteristics, expertise, or experiences.
- In-depth exploration: Purposive sampling allows for in-depth exploration of specific subgroups or characteristics, providing rich and detailed information.
Some disadvantages of purposive sampling are:
- Risk of bias: The researcher’s judgment introduces the potential for bias, as the selection process is subjective.
- Limited generalizability: Findings from purposive samples may have limited generalizability to the wider population, as participants are not randomly selected.
- Difficulty in defining criteria: Clearly defining the criteria for participant selection is crucial, and subjectivity in this process may affect the study’s validity.
List of recommended resources #
For a broad overview #
This article by Lauren Stweart on ATLAS.ti gives an overview of purposive sampling, its advantages and disadvantages as well as the scenarios in which to conduct purposive sampling.
This blog on Scribbr by Kassiani Nikolopoulou gives an overview of purposive sampling, a type of non-probability sampling. The blog explains when to use purposive sampling, different types of purposive sampling methods with examples along with a step-by-step guide for conducting purposive sampling.
For in depth understanding #
This paper reviews the various principles and practices of purposive sampling in implementation research. It also delineates the different types and categories of purposive sampling strategies as well as provides a list of recommendations for use.
This article by Chittaranjan Andrade thoroughly explains the concepts involved in convenience and purposive sampling with the help of examples of both good and bad sampling practices.
Case study #
This research paper aims to outline the intent and nature of purposive sampling. It presents three different case studies from different contexts – Co-led redesign of stroke services in North West Tasmania, Child and family health nurses and safety and wellbeing of young children, and How can mental wellbeing for new mothers be achieved? – to better illustrate the concept.
This article by Heather Ames, Claire Glention and Simon Lewin aims to present the development and application of a sampling framework (purposive sampling) for a qualitative evidence synthesis on vaccination communication.