Phenomena of interest to researchers in industrial and organizational (I-O) psychology and allied fields (e.g., human resource management, organizational behavior, organization theory) can be studied through research that uses a wide variety of design options. In this chapter, research design is defined as a unique combination of research setting and research strategy. The research design concept is defined somewhat differently in other works (e.g., Kerlinger, 1986;Runkel and McGrath, 1972;Stone, 1978). For example, Kerlinger defines research design as "the plan and structure of investigation so conceived as to obtain answers to research questions" (1986, p. 279); Runkel and McGrath note that research design is "a plan by which you will be able to reason, step by step, from the observations you [the researcher] intend to make to logically sound conclusions about problems or questions you are trying to resolve" (1972, p. 36). Rosenthal and Rosnow define design as "a blueprint that provides the scientist with a detailed outline or plan for the collection and analysis of data" (1991, p. 69).In any given study, the researcher must choose from among options concerning such factors as (a) research strategy (e.g., true experiment, quasi-experiment, non-experiment), (b) research setting (e.g., laboratory, field), research participants (e.g., students, workers, unemployed individuals), and (c) operational definitions of independent and dependent variables. The choices that are made about these factors influence the overall validity of conclusions that stem from a study Campbell, 1976, 1979;Cook, Campbell, and Peracchio, 1990;Kerlinger, 1986;Stone, 1978). As noted below, the overall confidence that a researcher has about the results of a study are a function of the validity of inferences about cause-effect relationships (internal validity), the correctness of statistical inferences derived from a study (statistical conclusion validity), the extent to which