7.2: The Classical Experiment

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Learning Objectives

Define classic experiments.
Identify the core features of classic experiments designs.
Describe the difference between an experimental group and a control group.

Several kinds of experimental designs exist. In general, designs considered to be classic experiments contain three key features: independent and dependent variables, pretesting and posttesting, and experimental and control groups. In the classic experiment, the effect of a stimulus is tested by comparing two groups: one that is exposed to the stimulus (the experimental group) and another that does not receive the stimulus (the control group). In other words, the effects of an independent variable upon a dependent variable are tested. Because the researcher’s interest lies in the effects of an independent variable, she must measure participants on the dependent variable before (pretest) and after (posttest) the independent variable (or stimulus) is administered. Thus pretesting and posttesting are both important steps in a classic experiment.

One example of experimental research can be found in Shannon K. McCoy and Brenda Major’s (2003)McCoy, S. K., & Major, B. (2003). Group identification moderates emotional response to perceived prejudice. Personality and Social Psychology Bulletin, 29, 1005–1017. study of people’s perceptions of prejudice. In one portion of this multifaceted study, all participants were given a pretest to assess their levels of depression. No significant differences in depression were found between the experimental and control groups during the pretest. Participants in the experimental group were then asked to read an article suggesting that prejudice against their own racial group is severe and pervasive, while participants in the control group were asked to read an article suggesting that prejudice against a racial group other than their own is severe and pervasive. Upon measuring depression scores during the posttest period, the researchers discovered that those who had received the experimental stimulus (the article citing prejudice against their same racial group) reported greater depression than those in the control group. This is just one of many examples of social scientific experimental research.

We will discuss other types of experiments shortly, but first we will discuss sampling in experiment.

KEY TAKEAWAY

Experiments are designed to test hypotheses under controlled conditions.