Sampling theory is a branch of statistics that focuses on obtaining information about a population from a smaller sample. It is used to understand the general characteristics of a population and to make inferences about the population as a whole. Sampling theory is important for accurately estimating population characteristics, such as the mean or the median, and for measuring the accuracy of the sample estimates.

The most common sampling technique is simple random sampling. In this technique, each member of the population has an equal chance of being selected for the sample. This ensures that the sample is representative of the population. Other sampling techniques include stratified sampling, clustered sampling, and systematic sampling.

Stratified sampling is used when the population is divided into distinct subgroups. This technique ensures that each subgroup is adequately represented in the sample. Clustered sampling is used when the population is divided into clusters, such as geographical areas or households. Systematic sampling is used when selecting members from a list or database, such as a telephone directory.

In addition to the selection of the sample, sampling theory also deals with the size of the sample. The size of the sample is determined by the amount of information needed and the variability of the population. Generally, the larger the sample, the more accurate the estimates will be.

In addition to the selection and size of the sample, sampling theory also considers the analysis of the sample data. This includes estimating the population characteristics, such as the mean or the median, and testing for statistical significance.

Sampling theory is an important part of statistics and is used in many different fields, including marketing, economics, and social science research. It is important to understand the principles of sampling theory in order to accurately and effectively collect data and make accurate inferences about a population.

References

Bryman, A., & Cramer, D. (2011). Quantitative research methods and statistics in psychology. London: Sage.

Cochran, W. G. (1977). Sampling Techniques (3rd ed.). New York: John Wiley & Sons.

Salkind, N. J. (2010). Statistics for people who (think they) hate statistics (4th ed.). Thousand Oaks, CA: Sage.