Probability and nonprobability are the two general categories of sampling. Probability sampling uses random selection, whereas nonprobability sampling does not. For example, if you wanted to study the effects of divorce on the psychological development of adolescents, you could gather a population of a certain number of adolescents whose parents were divorced. Then, out of that population, you could randomly select 25 of those people. If you wanted to use nonprobability sampling, you would choose specific people who had met predetermined criteria. Consider your own proposed study: Which of these sampling techniques might be best for your purposes?