Experimental and Quasi-Experimental Designs

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Experimental designs

Experimental designs are viewed as the most accurate, and most demanding of research designs, requiring strict attention to rules and procedures. Researchers use these research designs to manipulate and control testing procedures as a way to understand a cause and effect relationship. Commonly, independent variables are manipulated to judge or decide their effect on a dependent variable (Trochim & Donnelly, 2008).

In order for an experiment to be considered a true experimental design, the design must fit specific criteria. The researcher must have a hypothesis for a cause and effect relationship between variables, the treatment group, the control group, random selection for the treatment group, and random assignment for the control group. In a simple experiment, the researcher forms two groups that are similar or equivalent, through probability, to each other in every way possible appropriate to the concept of experiment. The treatment group receives the procedure for the experiment and the control group does not. Therefore, the only difference between the groups will be that one group receives the treatment for the experiment and one group does note. After the experiment is conducted the researcher analysis the results in both groups.

An important part of an experiment is random assignment. If the participants for the study are randomly assigned to create two groups, and the researcher has enough participants in the study to have the desired “probabilistic equivalence” (Trochim & Donnelly, 2008, p. 187) then the researcher will feel a sense of confidence that the study will have internal validity in order to assess whether or not the treatment caused the outcome hypothesized. Well-c...

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...not possible to construct (Experiment-Resources.com, 2010).

Experiments and research

The measure of the dependent variable is a significant element in experimental and quasi-experimental designs and allows for comparison of groups. Both designs can show probability of cause and effect relationships, which is important in research (Writing @ CSU, 2010).

Experiment-Resources.com. (2010, July). Types of research design. Retrieved July 17, 2010, from

Experiment- Resources.com: http://www.experiment-resources.com/true-experimental-design.html#ixzz0u5wQkp6b

Trochim, W. M., & Donnelly, J. P. (2008). The research methods knowledge base. Mason, OH: Cengage.

Writing @ CSU. (2010). Differences between experimental and qausi-experiment research. Retrieved July

19, 2010, from Writing @ CSU: http://writing.colostate.edu/guides/research/experiment/pop3e.cfm

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