Non-probability Sampling Methods in Qualitative and Exploratory Research
Non-probability Sampling Methods in Qualitative and Exploratory Research
Non-probability sampling techniques involve selecting participants based on the statistician’s capabilities rather than a predefined criterion. The non-probability sample selection implies that group members do not have the same probability of being selected to participate in the study. Although non-probability sampling is cheaper and easier to conduct, it has greater risks of human bias and does not accommodate sampling errors. The sampling methods are mostly used in qualitative and exploratory research to gain an initial understanding of a population that has not been adequately researched before. Non-probability sampling methods include:
(a). Convenience sampling techniques
A convenience sample is based on how easy it is for the researcher to access the participants. The selection is based on proximity rather than representativeness. Although convenience sampling is a cheap and easy way to gather data, especially at the initial data collection stages in research, it cannot produce generalizable results because there is no proof that the sample represents the target population. The non-probability sampling technique is used in cases where there are time and cost constraints in data collection.
Market researchers can use convenience sampling methods to survey the customers who visit a particular mall. They can do so by issuing questionnaires to the customers to fill out to understand their purchasing behavior. However, because the researcher may stand at the entrance or exit to survey the few customers who pass by, there is no way they can generalize their findings to the entire population of buyers.
(b). Purposive sampling methodology
In judgmental sampling, also known as purposive sampling, the researcher uses his expertise and knowledge of the target audience to select a sample that is most helpful to accomplish the purpose of the study. The method of sampling is mostly used in qualitative research involving a small specific population. Judgment sampling helps scholars and researchers gain detailed knowledge about a phenomenon rather than making statistical inferences. The desired sample size is selected based on defined criteria.
For instance, if a researcher wants to understand the thought patterns and opinions of expectant women about maternity experience, the sample frame would include only the expectant women. Those who are not pregnant are excluded from the study.
(c). Snowball sampling techniques
Snowball sampling is used when the target population is inaccessible, or the participants are hardly traceable. One uses snowballs to recruit other participants for the study. In such a case, the researchers can interview a few categories who are reachable to generate results. For instance, in a study that involves a sensitive topic like HIV/AIDs, subjects may not be willing to participate openly. One can use snowball sampling to survey the few volunteers who can link the researcher to other victims they may know.
(d). Quota sampling methods
The selection of participants in quota sampling depends on a pre-test standard or specific attributes. The technique operates under the assumption that the sample has the same qualities as the total population.
