sampling
n. the process of selecting for study a limited number of units from a larger set. The term most often refers to the selection of respondents, observations, or cases for inclusion in experiments, surveys, interviews, or other research. However, sampling can also involve selecting theoretical constructs to study, selecting measurement instruments from a broad set of potential options, or selecting time points at which to observe individuals or cases. There are various different selection methods, including simple random sampling, stratified sampling, convenience sampling, and quota sampling. Each approach has a different potential of obtaining a sample appropriately representative of the population under study.