ABSTRACT
This chapter alerts the reader to the importance of case selection and shows some basic principles that will help in the selection of cases in ways that will allow a clean examination of the research question. In random sampling, it is purely a matter of chance which cases from the full population end up in the sample for observation; that is, each member of the population has an equal chance of being drawn for the sample. If the reader wants to draw a random sample of a population, he/she needs a list of everyone in the population to sample and a list of random numbers. When a large population is involved, various methods exist to draw quasi-random approximations to a random sample. A purposive sample does not attempt to replicate the full population. Rather, it draws subjects to maximize variation in the independent variable of interest, so that the relationships looked for will be very clear.
