The goal of the experimental method is to provide more definitive conclusions about the causal relationships among the variables in a research hypothesis than what is available from correlational research. Experiments are designed to test hypotheses, or specific statements about the relationship between variables. Experiments are conducted in a controlled setting in an effort to explain how certain factors or events produce outcomes. A variable is anything that changes in value. In the experimental research design, the variables of interest are called the independent variable and the dependent variable. The independent variable in an experiment is the causing variable that is created or manipulated by the experimenter. The dependent variable in an experiment is a measured variable that is expected to be influenced by the experimental manipulation.

A good experiment randomly assigns participants to at least two groups that are compared. The experimental group receives the treatment under investigation, while the control group does not receive the treatment the experimenter is studying as a comparison. For instance, to assess whether violent TV affects aggressive behavior the experimental group might view a violent television show, while the control group watches a non-violent show. Additionally, experimental designs control for extraneous variables, or variables that are not part of the experiment that could inadvertently effect either the experimental or control group, thus distorting the results.

Despite the advantage of determining causation, experiments do have limitations. One is that they are often conducted in laboratory situations rather than in the everyday lives of people. Therefore, we do not know whether results that we find in a laboratory setting will necessarily hold up in everyday life. Second, and more important, is that some of the most interesting and key social variables cannot be experimentally manipulated because of ethical concerns. If we want to study the influence of abuse on children’s development of depression, these relationships must be assessed using correlational designs because it is simply not ethical to experimentally manipulate these variables. Characteristics of descriptive, correlational, and experimental research designs can be found in Table 1.5.