In probability theory and statistics, sampling is the selection of individuals from a population of interest (or the collection of data on those individuals). A sampling frame is the actual list that a sample is drawn from.

Methods of statistical sampling include:

• simple random sampling
• systematic sampling
• stratified sampling
• cluster sampling
• multistage sampling

These are all examples of probability sampling, or random sampling, in which the probability of getting any particular sample may be calculated based on a probability model.

A sampling method that does not meet this criterion is called nonprobability sampling. Nonprobability sampling techniques should be used to infer from the sample to the general population only with great caution. An example of nonprobability sampling is convenience sampling, in which members of the population are chosen based on their relative ease of access.

See also : statistics, marketing research, quantitative marketing research, cluster sampling, multistage sampling, simple random sampling, nonprobability sampling, systematic sampling, stratified sampling