CONSTRUCTING LABORATORY EXPERIMENTS
The preceding chapter discussed the design of experimental studies at a relatively abstract level to introduce basic principles of planning and constructing a laboratory experiment. This chapter considers how to implement an experimental design, in terms of the basic construction of a laboratory experiment, and describes the different forms of experimental treatments that are used in contemporary social research. The chapter also covers aspects of the experiment that, while not formal features of the design, can nevertheless have a great impact on a study's outcome. Although this text is not meant to be a nuts and bolts “how to do it” book, this chapter contains details and information that should provide a useful guide to the conduct of experimental research.
Figure 5.1 presents a skeletal framework for constructing a laboratory experiment, outlining the elements that comprise any experimental study. In developing an experiment, the researcher in effect creates an “alternate universe, ” a small but self-contained environment in which the main “action” of the study takes place. Each step in the construction has to be defined and controlled by the experimenter, and this control constitutes an important feature, both the strength and the weakness, of the experimental method.
The first step in developing any study is arranging for the availability of a pool of eligible participants. This is the essential first step because it will control many of the later decisions the experimenter must make, including the particular form of treatment, the measures to be used, the extent to which the researcher is a part of the experimental context, and so on. This step also may be one of the most difficult for the experimenter to control. (We discuss some of the ways in which participants may be recruited for participation in experiments later in this chapter). At this point, we assume that a pool of participants is potentially available for the study. It is the researcher's role to define which participants are eligible to take part in the investigation. For some purposes, for practical or theoretical reasons, the researcher may wish to limit the investigation to individuals with particular characteristics, such as only male participants or only those of a specific age range, race, or religion. In