The sampling procedure has a significant impact on a study's accuracy. An overview of the different sampling strategies used in research is given in the chapter. These methods fall into two general categories: non-probability sampling methods and probability sampling methods. Simple random sampling, systematic random sampling, cluster sampling and stratified random sampling are examples of probability sampling procedures. However, quota sampling, self-selection sampling, convenience sampling, snowball sampling, and purposive sampling are examples of non-probability sampling methods.