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# Probability Sampling

Part 2. Marketing Research

1. Richard J. Fox

Published Online: 15 DEC 2010

DOI: 10.1002/9781444316568.wiem02054

## Wiley International Encyclopedia of Marketing

#### How to Cite

Fox, R. J. 2010. Probability Sampling. Wiley International Encyclopedia of Marketing. 2.

#### Author Information

1. University of Georgia, Athens, GA, USA

#### Publication History

1. Published Online: 15 DEC 2010

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### Abstract

Sampling involves the selection of a subset from a population, and making inferences pertaining to the population based on information from the sample. Probability sampling refers to sampling methods in which chance or randomness is involved in the sample selection process. Each element in the population from which the sample is to be selected has a positive probability of being included in the sample. Probability sampling is the basis for the statistical calculation of the potential error associated with an estimate of a population parameter developed from sample data. Simple random sampling is the most basic form of probability sampling. A simple random sample of size n is selected in such a way that all subsets of size n are equally likely to be the sample selected. The probability that any single item is included in the sample when simple random sampling is used is the ratio of the sample size to the population size. This is the type of sampling that is typically assumed when making basic statistical calculations regarding the precision of sample estimates. For example, the typical 95% confidence interval associated with an estimate is based on the assumption that simple random sampling was used to select the sample. There are more sophisticated forms of probability sampling than simple random sampling, and different statistical calculations are required to determine the precision of estimates when these alternative forms of probability sampling are used. It is obviously important in practice to make sure that the statistical precision calculations are appropriate for the type of probability sampling used.

### Keywords:

• confidence interval;
• simple random sampling;
• unbiased;
• statistical precision;
• probability sampling