Purposive sampling also known as judgmental, selective, or subjective sampling, reflects a group of sampling techniques that rely on the judgment of the researcher. Unlike random sampling, where researchers give each individual an equal selection chance, purposive sampling involves selecting individuals who can provide valuable insights into the research topic.
This sampling procedure is always the first choice of the researcher. Judgmental sampling is completely opposite of probability sampling such as simple random sampling, stratified sampling, systematic sampling, cluster sampling, and multi-stage sampling. So purposive sampling is a non-probability sampling.
Why Use Purposive Sampling?
Purposive sampling is commonly used in qualitative research where the goal is to gain deep understanding rather than generalizability. Researchers use this method when they need specific insights from experts, key informants, or particular groups that align with their study objectives.
According to Wikipedia,
“Judgment sample, or Expert sample, is a type of random sample that is selected based on the opinion of an expert. Results obtained from a judgment sample are subject to some degree of bias, due to the frame and population not being identical. The frame is a list of all the units, items, people, etc., that define the population to be studied. Judgment sampling is noble to provide detailed information about the difficulties in obtaining the distinction. A random sample would provide less bias, but potentially less raw information. The downfalls of this system are significant as any non-random sample brings bias into question, which limits the types of statistical analyses you may reasonably perform, and there are considerable limits to an expert’s ability to choose a good sample.”
Advantages of Purposive Sampling
- Focused Data Collection – Researchers select participants with direct relevance to the research question.
- Cost-Effective – Requires fewer resources compared to probability sampling methods.
- Efficient – Ideal for small-scale studies where in-depth data collection is needed.
- Applicable to Specialized Studies – Useful for niche topics where finding a representative sample is challenging.
More Precisely,
- It is a simple method of sampling.
- Systematic samples are convenient to draw and excuse.
- This method is comparatively economical in terms of time, labor, and money.
Disadvantages of Purposive Sampling
- Potential Bias – Researchers’ subjectivity may influence participant selection.
- Limited Generalizability – Findings may not be applicable to a broader population.
- Dependence on Researcher Expertise – The quality of the sample depends on the researcher’s ability to select appropriate participants.
More Precisely,
- This information doesn’t represent the population.
- Unwillingness to help and cooperate Selecting informants who are convenient for the study.
- Sampling bias always exists in this sampling.
Types of Purposive Sampling
Several variations of purposive sampling exist, each serving different research needs:
1. Expert Sampling
- Involves selecting individuals with specialized knowledge or expertise in a particular field.
- Example: Interviewing medical professionals about new treatment methods.
2. Homogeneous Sampling
- Focuses on participants who share similar traits or experiences.
- Example: Studying the effects of online learning among university students.
3. Heterogeneous (Maximum Variation) Sampling
- Aims to capture diverse perspectives by selecting participants with different characteristics.
- Example: Investigating opinions on climate change from people across various age groups and professions.
4. Critical Case Sampling
- Selects participants who can provide crucial insights or serve as representative examples.
- Example: Analyzing the impact of policy changes on a small business directly affected by new regulations.
- Involves existing participants referring other potential participants, making it useful for reaching hard-to-find populations.
- Example: Conducting research on individuals who have experienced a rare medical condition.
6. Extreme or Deviant Case Sampling
- Focuses on unusual or outlier cases to explore unique situations.
- Example: Studying exceptionally successful entrepreneurs in a declining industry.
7. Typical Case Sampling
- Selects individuals who represent average or typical cases within a population.
- Example: Examining the daily work-life balance of an average office worker.
And also Quota Sampling is another type of Purposive Sampling.
Examples of Purposive Sampling in Research
- Healthcare Research: Doctors and nurses are selected to provide insights into patient care.
- Educational Studies: Teachers and students from a particular school are chosen to assess new learning methods.
- Business and Marketing: Customer feedback is gathered from a targeted group with specific buying behaviors.
Conclusion
Purposive sampling is a powerful tool in qualitative research, enabling researchers to select participants strategically for meaningful insights. While it has limitations in generalizability, it is highly effective for exploratory and specialized studies. Understanding the different types of purposive sampling allows researchers to choose the best approach for their study goals.
By applying purposive sampling effectively, researchers can ensure their studies provide valuable, focused, and actionable data that drives meaningful conclusions.
Q&A
Q1: Is purposive sampling qualitative or quantitative?
A: Purposive sampling is primarily used in qualitative research where in-depth insights are needed rather than numerical data.
Q2: What is the main difference between purposive and random sampling?
A: The key difference is that purposive sampling selects participants based on specific criteria, while random sampling gives all individuals an equal chance of being selected.
Q3: When should purposive sampling be used?
A: It should be used when researchers need targeted insights from specific individuals, such as experts or groups with unique experiences.
Q4: Can purposive sampling be biased?
A: Yes, since participants are selected deliberately, there is a potential for researcher bias, which may affect the study’s objectivity.
Q5: Is purposive sampling generalizable?
A: No, since it is a non-probability sampling method, the results are typically not generalizable to the entire population.