Convenience Sampling

Convenience sampling is a type of nonprobability sampling in which people are sampled simply because they are “convenient” sources of data for researchers. In probability sampling, each element in the population has a known nonzero chance of being selected through the use of a random selection procedure. Nonprobability sampling does not involve known nonzero probabilities of selection. Rather, subjective methods are used to decide which elements should be included in the sample. In nonprobability sampling, the population may not be well denned. Nonprobability sampling is often divided into three categories: purposive sampling, convenience sampling, and quota sampling.

Convenience sampling differs from purposive sampling in that expert judgment is not used to select a representative sample of elements. Rather, the primary [Page 149]selection criterion relates to the ease of obtaining a sample. Ease of obtaining the sample relates to the cost of locating elements of the population, the geographic distribution of the sample, and obtaining the interview data from the selected elements. Examples of convenience samples include mall intercept interviewing, unsystematically recruiting individuals to participate in the study (e.g. what is done for many psychology studies that use readily available undergraduates), visiting a sample of business establishments that are close to the data collection organization, seeking the participation of individuals visiting a Web site to participate in a survey, and including a brief questionnaire in a coupon mailing. In convenience sampling the representativeness of the sample is generally less of a concern than in purposive sampling.

For example, in the case of a mall intercept survey using a convenience sample, a researcher may want data collected quickly using a low-cost method that does not involve scientific sampling. The researcher sends out several data collection staff members to interview people at a busy mall, possibly on a single day or even across a weekend. The interviewers may, for example, carry a clipboard with a questionnaire that they may administer to people they stop in the mall or give to people to have them fill out. This variation in convenience sampling does not allow the researcher (or the client) to have any sense of what target population is represented by the sample. Although convenience samples are not scientific samples, they do on occasion have value to researchers and clients who recognize their severe limitation; for example, they may allow some quick exploration of a hypothesis that the researcher may eventually plan to test using some form of probability sampling.