ever, research design (and corresponding scientific methods) is a crucial aspect of science. It is also the subject of much debate in many fields, including education. In this chapter, we describe some of the most frequently used and trusted designs for scientifically addressing broad classes of research questions in education.
In doing so, we develop three related themes. First, as we posit earlier, a variety of legitimate scientific approaches exist in education research. Therefore, the description of methods discussed in this chapter is illustrative of a range of trusted approaches; it should not be taken as an authoritative list of tools to the exclusion of any others.1 As we stress in earlier chapters, the history of science has shown that research designs evolve, as do the questions they address, the theories they inform, and the overall state of knowledge.
Second, we extend the argument we make in Chapter 3 that designs and methods must be carefully selected and implemented to best address the question at hand. Some methods are better than others for particular purposes, and scientific inferences are constrained by the type of design employed. Methods that may be appropriate for estimating the effect of an educational intervention, for example, would rarely be appropriate for use in estimating dropout rates. While researchers—in education or any other field—may overstate the conclusions from an inquiry, the strength of scientific inference must be judged in terms of the design used to address the question under investigation. A comprehensive explication of a hierarchy of appropriate designs and analytic approaches under various conditions would require a depth of treatment found in research methods textbooks. This is not our objective. Rather, our goal is to illustrate that among available techniques, certain designs are better suited to address particular kinds of questions under particular conditions than others.
Third, in order to generate a rich source of scientific knowledge in education that is refined and revised over time, different types of inquiries and methods are required. At any time, the types of questions and methods depend in large part on an accurate assessment of the overall state of knowl-