ABSTRACT
This chapter discusses how to use probability sampling to conduct surveys. In a probability sample, each unit in the population has a known probability of selection, and a random number table or other randomization mechanism is used to choose the specific units to be included in the sample. If a probability sampling design is implemented well, an investigator can use a relatively small sample to make inferences about an arbitrarily large population. Simple random sampling is the most basic form of probability sampling, and provides the theoretical basis for the more complicated forms. In the model-based approach, the probability model is proposed for all population units, whether in the sample or not. The expected value of the statistic is the weighted average of the possible sample values of the statistic, weighted by the probability that particular value of the statistic would occur.
