In a quasi-experimental design, the research substitutes statistical "controls" for the absence of physical control of the experimental situation. The most common quasi-experimental design is the Comparison Group Pre-test/Post-test Design. This design is the same as the classic controlled experimental design except that the subjects cannot be randomly assigned to either the experimental or the control group, or the researchers cannot control which group will get the treatment. In other words, participants do not all have the same chance of being in the control or the experimental groups, or of receiving or not receiving the treatment.
