ABSTRACT
This chapter looks at how researchers can develop a research question, measure the variables involved, and look for relationships among them to provide answers to the research question. It also shows some basic principles that help researchers to select cases in ways that allow them a clean examination of research question. The chapter deals with issues having to do with the following: the selection of cases; the question of sampling from a larger population; the problem of censored data; and the question of whether to select cases on the basis of what researchers are trying to explain or on the basis of their independent variable. Random sampling is a matter of chance which cases from the full population end up in the sample for observation. A purposive sample works only for the particular independent variable or variables based on the sample. Various methods exist to draw quasi-random approximations to a random sample when a large population is involved.
