Experimental design is a quantitative design that is unique because it determines causality. Causality determines cause and effect i.e. manipulation of X (independent variable) causes a change in the Y (Dependent or outcome variable). This lesson explains experimental design in details. We shall start by explaining the meaning of experimental design. As we have said in this introduction, experimental design is a quantitative design that measures causality.

The lesson will also discuss how causality is demonstrated. Causality is demonstrated by use equal numbers of two homogenous groups. One group is called the control group while the other group is the experimental group. Treatment is given to experimental while no treatment is given to control group. A pre-test and post test is given before and after the treatment respectively to determine whether a change has been brought about by the treatment or intervention.

To determine causality, two factors are key: ensure you avoid spurious relationships and control all extraneous variables. This lesson explains how to avoid a spurious relationship and how to control extraneous variables.

Finally, the lesson discusses the elements of an experimental designs and types of experimental procedures. There are two key types: true experimental design where randomization is feasible and quasi experimental where randomization is not feasible. Randomization means that every member of the population has an equal chance of being selected and assigned to either experimental and control group.