Probability Sampling

A sample in which every possible [observation]] in the population has a known and finite ratio of probability of inclusion in the population relative to every other unit in the population. The most common cases of this are where:

• Each possible observation in the population has a known and non-zero probability of being included in the sample.
• Each possible observation has an unknown but equal probability of inclusion.

The most common variants of probability sampling used in survey research are:

• Simple Random Sampling
• Stratified Random Sampling
• Cluster Sampling
• Multistage Sampling