Experimentation is the research technique that is at the core of scientific investigation because it offers the most powerful way to test causal relationships—that is, to determine that one variable (the treatment or independent variable) is truly affecting another (the outcome or dependent variable). This chapter includes two articles exemplifying one of the major kinds of experimental design: the laboratory experiment and the field experiment. In the first article, John Zipp’s classroom provides a good laboratory in which to examine the effectiveness of a teaching technique. The second article is an example of a field experiment in which researchers use a real-world setting. Field experiments involve either inserting some manipulation (the treatment variable) into the everyday course of events and then observing any influences on people’s behavior, or simply measuring the outcomes of a naturally occurring change in the social world.