What is a probability sample?
A probability sample is a sample where every element of the target population has a known, non-zero probability of being selected. That is, it is possible for every element of the target population to be in the sample. Two important features of a probability sample are that the probability selection mechanism (1) guards against site selection bias and (2) is the basis for scientific inference to characteristics of the entire target population. Many alternative approaches are available to select a probability sample. Which approach is used depends on the objectives of the survey, the available auxiliary information, logistical or operational constraints in conducting the sampling, the characteristics of the sample frame, and the complexity of the statistical analysis. A few alternative designs are described below. Go to Top Simple random sample. A simple example of a probability sample is one that gives every sample of a fixed size the same probability of being selected. This is simple
