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Probability sampling
Explanations > Social Research > Sampling > Probability sampling
Probability sampling is uses random selection to create the sample.
This is not always easy and care must be taken to ensure the probability of something appearing in the sample is the same probability as it also appearing in the population. This will never be exactly the same, but any variation should be due to statistical sampling error rather than a sample that is too small or where bias occurs in the selection process.
Methods of probability sampling include:
- Simple random sampling: Pure sample of population.
- Stratified sampling: Sample from separate groups.
- Systematic sampling: Use every nth person.
- Cluster sampling: Focus on a few groups.
Note that statistical analysis is generally based on the assumption of random samples. If the samples are not randomly chosen then statistical analysis may be invalid and give false results.
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