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Controlled Experiments

Determining Cause And Effect


Controlled experiments are very common in medical research and psychology research, although they can be used in sociological research as well. A controlled experiment is a highly focused way of collecting data and is especially useful for determining patterns of cause and effect.

Experimental Group And Control Group

To conduct a controlled experiment, two groups are needed: an experimental group and a control group. The experimental group is a group of individuals that are exposed to the factor being examined. The control group, on the other hand, is not exposed to the factor. It is imperative that all other external influences are held constant. That is, every other factor or influence in the situation needs to remain exactly the same between the experimental group and the control group. The only thing that is different between the two groups is the factor being researched.


If you were interested in studying whether or not violent television programming caused aggressive behavior in children, you could conduct a controlled experiment to investigate. In such a study, the dependent variable would be the children’s behavior while the independent variable would be exposure to violent programming. To conduct the experiment, you would expose an experimental group of children to a movie containing a lot of violence, such as martial arts or gun fighting. The control group, on the other hand, would watch a movie that contained no violence. To test the aggressiveness of the children, you would take two measurements: one pretest measurement made before the movies are shown, and one posttest measurement made after the movies are watched. Pretest and posttest measurements should be taken of both the control group and the experimental group.

Studies of this sort have been done many times and they usually find that children who watch the violent movies are more aggressive afterward than those who watch a movie containing no violence.

Strengths And Weaknesses

Controlled experiments have several strengths and weaknesses. Among the strengths is the fact that it can establish causation. That is, it can determine cause and effect between variables. It can also zero in on a single independent variable, since all other factors in the experiment are held constant.

On the downside, controlled experiments can be artificial. That is, they are done, for the most part, in a manufactured laboratory setting and therefore tend to eliminate many real-life effects. As a result, analysis of a controlled experiment must include judgments about how much the artificial setting has affected the results.


Andersen, M.L. and Taylor, H.F. (2009). Sociology: The Essentials. Belmont, CA: Thomson Wadsworth.

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