ABSTRACT
This chapter explores the mechanics of sampling—of choosing a relatively small number of cases that can provides accurate information about the larger population from which they have been selected. The advantage of sampling becomes clear when consider the potential cost and time required to study an entire population. The potential problems of biased samples were clearly illustrated in a public opinion polling disaster that befell a magazine called the Literary Digest. Probability sampling involves randomly selecting cases from a population so that the group selected as a sample is representative of the population from which it was drawn. The guiding principle underlying probability sampling is randomization. The technique of systematic random sampling has one major advantage over simple random sampling—ease of application to large populations that meet the criterion of central listing—and it has many potential uses. Six basic types of nonprobability samples: convenience samples, volunteer samples, purposive samples, snowball samples, quota samples, and judgmental samples.
