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Research Methods in the Social Sciences

Experimental Design*

Definition and Purpose

A blueprint of the procedure that enables the researcher to maintain control over all factors that may affect the result of an experiment. In doing this, the researcher attempts to determine or predict what may occur. Experimental Research is often used where there is time priority in a causal relationship (cause precedes effect), there is consistency in a causal relationship (a cause will always lead to the same effect), and the magnitude of the correlation is great. The classic experimental design specifies an experimental group and a control group. The independent variable is administered to the experimental group and not to the control group, and both groups are measured on the same dependent variable. Subsequent experimental designs have used more groups and more measurements over longer periods. True experiments must have control, randomization, and manipulation.

What do these studies tell you?

  1. Experimental research allows the researcher to control the situation. In so doing, it allows researchers to answer the question, “what causes something to occur?”
  2. Permits the researcher to identify cause and effect relationships between variables and to distinguish placebo effects from treatment effects.
  3. Experimental research designs support the ability to limit alternative explanations and to infer direct causal relationships in the study.
  4. Approach provides the highest level of evidence for single studies.

What these studies don't tell you?

  1. The design is artificial, and results may not generalize well to the real world.
  2. The artificial settings of experiments may alter subject behaviors or responses.
  3. Experimental designs can be costly if special equipment or facilities are needed.
  4. Some research problems cannot be studied using an experiment because of ethical or technical reasons.
  5. Difficult to apply ethnographic and other qualitative methods to  experimental designed research studies.


Sample Experimental Studies