Abstract

This chapter provides an overview of experimental and quasi-experimental methods with a particular focus on experimental techniques that provide alternatives to the randomized controlled study which is, in effect in terms of the hierarchy of evidence described in Chapter 3, a particularly form of experimental method. The principles of the double blind controlled trial, where randomization can control for confounding variables and double-blinding can reduce certain types of bias, have been described in the previous chapter. However, it is not always possible to conduct an RCT for methodological, practical and ethical reasons that are discussed below. What are broadly termed experimental methods, an umbrella term that includes a wide variety of particular techniques, aim to maintain scientific rigour in situations where it is not possible to set up controls. The chapter will explain the language of experimentation and discuss the advantages and disadvantages, as well as how such methods should be applied. A range of experimental research designs based on published or unpublished studies are described to illustrate the use of this method in practice.