Purposive Sampling

Purposive sampling is a research tool that applies a non-random sampling technique to select specific individuals or cases that possess the desired characteristics or qualities relevant to the study's objectives. It focuses on selecting participants who can provide deeper insights or represent unique perspectives that are crucial for the research questions or goals.

This method is beneficial in studies where the emphasis is on depth of understanding. It enables a more targeted and detailed exploration of a specific phenomenon or circumstance. However, it may produce a level of prejudice as the sample is not on the basis of random selection.

• Purposive sampling is a research instrument that uses a non-random sampling approach to pick particular people or instances that fit the study's goals and exhibit the necessary traits.
• This approach works well for studies where comprehending complexity is a priority. This method makes it viable to investigate an event or scenario in more detail and with better clarity.
• However, finding eligible participants who fit the specified requirements can be challenging. This procedure may necessitate meticulous screening and assessment to ensure that the individuals chosen are appropriate for the research.

Purposive sampling, also known as selective, judgmental, or subjective sampling, is a non-probability sampling method that involves an intentional and strategic selection of specific participants with unique characteristics or qualities that are vital to the research objectives. It is based on the deliberate selection of participants who can offer in-depth insights, specialized knowledge, or distinct perspectives that are important for the study.

Researchers employ this method when seeking particular traits, experiences, or information that align with the research questions or objectives. It is valuable in studies where the significance is on obtaining an extensive and rich understanding of an occurrence. The process allows researchers to concentrate on specific groups or individuals, which makes it ideal for studies exploring niche or specialized topics. However, careful consideration of the research objectives, the nature of the study, and potential biases are crucial when opting for this sampling, as these factors can substantially influence the conclusions drawn from the research.

The characteristics of purposive sampling in research include the following:

• This sampling involves a conscious, systematic selection of specific individuals or cases based on predetermined criteria. Researchers choose participants who possess particular traits, experiences, or information suitable to the study.
• The selection process closely aligns with the research goals. Researchers choose participants who can offer specialized knowledge or unique experiences associated with the specific research questions, which enables an in-depth exploration of the topic.
• The method allows for flexibility in participant selection. Researchers can adapt their approach throughout the study. They may keep refining the criteria or selecting new participants to ensure a comprehensive exploration of the research topic.
• Since it is a non-random selection process, the sampling process may introduce bias into the sample. 

Some types of purposive sampling are:

• Maximum Variation Sampling: This approach involves deliberately selecting participants who exhibit diverse characteristics or experiences related to the research topic. It helps capture a wide range of viewpoints and ensures a comprehensive understanding of the subject matter.
• Homogeneous Sampling: The method involves selecting participants who share similar traits or perspectives relevant to the research. It enables researchers to study deeply about a specific issue by selecting a group with similarities.
• Criterion-Based Sampling: Here, researchers choose the participants based on specific criteria defined by them. The selection criteria may encompass particular qualifications, attributes, behaviors, or characteristics that directly relate to the research goals.
• Expert Sampling: This type involves selecting individuals or cases considered experts in a particular field. These experts help provide critical insights that aid in enhancing the depth and quality of information in the study.
• Typical Case Sampling: Researchers select participants who represent the typical or common characteristics of the larger population under study. This method aims to capture the average or standard attributes that are prevalent within the group.

Let us go through the following examples to understand this sampling technique:

Example #1

Suppose Ryan is a researcher investigating the spending habits of wealthy millennials in urban areas. He employed a purposive sampling strategy where he deliberately selected participants who were between 25 and 35 years old, living in major cities, and earning above a specific income limit.

This targeted selection allowed the study to focus specifically on individuals who are likely to have significant disposable income and specific consumption patterns. Ryan gained insights into the distinct financial behaviors, investment tendencies, and spending preferences of this particular demographic by choosing participants based on specific criteria that are appropriate for his research topic.

Example #2

A study was carried out with the goal of developing and evaluating an educational program for reducing moral distress in nurses. Moral distress affects nurses, patients, and healthcare systems negatively and is a prevalent problem. In February 2021, a three-phase mixed-method study was conducted in Shiraz, Iran.

Six Program of Reducing Moral Distress (PRMD) participants were chosen by purposive sampling for a content analysis study. The study discovered that the reasons for moral discomfort were a lack of professional competency, a weak organizational culture, personal factors, environmental and organizational aspects, managerial issues, and nurses' observation of ethical issues.

The advantages of purposive sampling are as follows:

• One of the primary advantages of purposive sampling is it allows researchers to select participants depending on specific criteria that are related to the study. This targeted approach ensures that the chosen participants possess the necessary characteristics, experiences, or knowledge crucial to address the research objectives.
• It allows for a more profound investigation into a specific phenomenon. Researchers can look deeply into the subject matter and generate comprehensive and rich data. This depth aids in understanding complex issues with clarity and detail.
• Researchers have the flexibility to refine the selection criteria during the study. This adaptability enables adjustments in the selection process and facilitates the inclusion of additional participants or modification of criteria if necessary.
• This method can be cost-effective because it focuses efforts on specific individuals or cases. It results in efficient utilization of resources, which reduces the costs associated with data collection and analysis.

The disadvantages of purposive sampling are:

• The subjective nature of participant selection may introduce bias. Researchers may overlook other relevant perspectives or characteristics, which may alter the results and impact their quality.
• One of the significant disadvantages of purposive sampling is that the sample may not be representative of the broader population. It may hinder the application of the results beyond the selected group.
• Identifying suitable participants who meet the defined criteria can be challenging. This process may require extensive screening and evaluation to ensure that selected participants genuinely align with the research objectives.

The differences between them are as follows:

Purposive Sampling

• This sampling involves the intentional selection of participants based on specific characteristics that are pertinent to the research objectives. Researchers deliberately choose individuals or cases that possess qualities, knowledge, or experiences crucial to the study.
• This method focuses on depth and enables an in-depth and detailed exploration of the subject matter.
• However, the method's subjective nature may result in biased findings.

Convenience Sampling

• Convenience sampling involves the selection of readily available participants who are easily accessible or convenient for the researcher.
• It is a non-probability sampling method that does not require a specific selection criterion. The method relies on accessibility and immediate availability.
• The method often leads to a biased sample due to its non-random nature.

Criterion Sampling

• Criterion sampling involves selecting participants who meet specific criteria defined by the researcher. These criteria can include particular qualifications, characteristics, behaviors, or experiences that directly relate to the research objectives.
• This method ensures that participants meet predefined standards and focuses on a more specific subset of the population that matches the required criteria.
• This technique might limit the diversity of perspectives and overlook relevant information that is beyond the set criteria.

This article has been a guide to what is Purposive Sampling. We explain its examples, advantages, types, & comparison with convenience & criterion sampling. You may also find some useful articles here -

• Data Sampling
• Random Sampling
• Data Collection