Sampling Methods
Terms
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- A sample selected in some fashion other than those suggested by probability theory.
- nonprobability sample
- A probability sampling procedure in which each element has an equal chance of selection independent of any other event in the selection process.
- random selection
- The unwarranted generalization of research findings to the population as a whole when one gender is not adequately represented in the research sample.
- gender bias
- A type of nonprobability sample in which we select the units to be observed on the basis of our own judgment about which ones will be the most useful or representative. Another name for this is purposive sample.
- judgmental sample
- A summary statistic describing a given variable in a population, such as the mean income of all families in a city or the age distribution of the city's population.
- parameter
- A form of multistage cluster sample in which geographic areas such as census blocks or tracts serve as the first-stage sampling unit. Units selected in the first stage of sampling are then listed—all the households on each selected block would be written down after a trip to the block—and such lists would be sub sampled.
- area probability sample
- A sample drawn using cluster sampling procedures.
- cluster sample
- A sample design in which each member of a population has the same chance of being selected into the sample.
- equal probability of selection method (EPSEM)
- A type of nonprobability sampling in which cases selected for observation are those that are not thought to fit the regular pattern. For example, the deviant cases might exhibit a much greater or lesser extent of something.
- deviant case sampling
- The group or collection that a researcher is interested in generalizing about. More formally, it is the theoretically specified aggregation of study elements.
- population
- A sampling method that selects elements simply because of their ready availability and convenience. Frequently used in social work because it is usually less expensive than other methods and because other methods may not be feasible for a particular type of study or population.
- availability sampling
- The general term for a sample selected in accord with probability theory, typically involving some random selection mechanism. Specific types of probability samples include area probability sample, EPSEM, PPS, simple random sample, and systematic sample.
- probability sample
- That unit in a sample about which information is collected and that provides the basis of analysis. Typically, in survey research, elements are people or certain types of people.
- element
- This refers to a type of multistage cluster sample in which clusters are selected, not with equal probabilities (see equal probability of selection method) but with probabilities proportionate to their sizes—as measured by the number of units to be sub sampled.
- probability proportionate to size (PPS)
- That quality of a sample of having the same distribution of characteristics as the population from which it was selected. By implication, descriptions and explanations derived from an analysis of the sample may be assumed to represent similar ones in the population.
- representativeness
- A type of nonprobability sample in which units are selected into the sample on the basis of prespecified characteristics so that the total sample will have the same distribution of characteristics as are assumed to exist in the population being studied.
- quota sampling
- The use of random sampling techniques that allow a researcher to make relatively few observations and generalize from those observations to a much wider population.
- probability sampling
- A multistage sampling procedure in which natural groups (clusters) are sampled initially, with the members of each selected group being sub sampled afterward.
- cluster sampling
- Selecting a sample of observations that the researcher believes will yield the most comprehensive understanding of the subject of study, based on the researcher's intuitive feel for the subject that comes from extended observation and reflection.
- purposive sampling