Which of the following is NOT a sampling method?

Qualitative sampling is characterized by the selection of participants based on specific traits or characteristics relevant to the research, rather than following a predefined probability sampling method. In contrast, the other options listed—random sampling, stratified random sampling, and cluster sampling—are all established probability sampling methods. These methods involve systematic techniques that allow for random selection, enabling researchers to generalize findings from a sample to a larger population.

Random sampling entails selecting individuals from a population entirely at random, ensuring every individual has an equal chance of being chosen. Stratified random sampling divides the population into distinct subgroups (or strata) based on specific characteristics before randomly sampling from each stratum, ensuring representation from all segments. Cluster sampling involves dividing the population into clusters, usually geographically, and then randomly selecting entire clusters to include in the sample.

In contrast, qualitative sampling lacks these systematic approaches and often focuses on depth of information from a limited number of cases, making it more exploratory in nature. This distinction clearly identifies qualitative sampling as the method that does not fit within the boundaries of established sampling methods.