Convenience sampling is also known as grab, opportunity, accidental or haphazard sampling. With this method, the researcher uses subjects that are easy to reach. As the name describes, the researcher chooses subjects because of convenience. Some examples of convenience sampling are when students use their classmates in a research study or a television reporter interviews people on the street.
In research methods, there are two primary classifications for sampling methods: nonprobability and probability. With probability sampling methods, all possible subjects out of a population have some chance of being included in the sample. Researchers can even calculate the mathematical probability of one of them being selected. They can also calculate sampling error, which is the degree to which the sample might differ from the actual population.
Convenience sampling is a nonprobability method. This means that subjects are chosen in a nonrandom manner, and some members of the population have no chance of being included. With nonprobability sampling, researchers have no way of calculating how well their sample represents the population as a whole. In general, probability sampling is considered to be more stringent and accurate than nonprobability sampling, but it is not always feasible.
When time or cost is a factor, some researchers might use convenience sampling. It is often used in pilot or exploratory studies when the researcher wants an inexpensive and quick way to discern whether further research is warranted. Many social science studies use convenience sampling with students, paid volunteers or clients.
Another method that is similar to convenience sampling is called snowball sampling. This is another nonprobability method, in which current participants refer or identify other possible subjects. Snowball sampling is often used when members of a particular population are difficult to find.
There are obvious benefits to convenience sampling. It usually is a quick and relatively cost-effective method of gathering data. Many researchers already have a pool of clients, patients, students, colleagues or friends they can utilize.
Random sampling, a probability method, is considered the gold standard for research. With random sampling, every member of the population has an equal chance of being selected, thus the sample is a good representation of the population. A convenience sample is not representative of the population, and the method is not as structured or rigorous as probability methods. Studies that utilize this method of sampling should be evaluated critically for possible bias and limits on generalization of the results.