This chapter discusses the basics of experimental design used in media studies research. Many scientific researchers believe, with good reason, that the controlled experiment is perhaps the best research method for determining a cause and effect relationship between variables. The chapter considers the types of research questions experiments can address, how the experiment can demonstrate causal relationships between variables, common experimental designs, data collection and interpretation, and ethical considerations. A major part of the chapter deals with internal validity pitfalls, such as confounds, randomization, and how to determine acceptable sample sizes. It also considers what may be regarded as controversial issues in experimental research, such as generalizability (or lack thereof), how to create treatment variance, the issues involved with creating message variance, and handling the issues of design complexity and manipulation checks.