Experimental Designs Experimental designs are considered the most thorough and demanding research projects, requiring rigorous 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 meet specific criteria. The researcher must have a hypothesis for a cause and effect relationship between variables, treatment group, 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, in probability, to each other in every possible way appropriate to the concept of the 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 the other group notes it. After conducting the experiment, the researcher analyzes the results in both groups. An important part of an experiment is random assignment. If study participants are randomly assigned to create two groups and the researcher has a sufficient number of study participants to achieve the desired “probabilistic equivalence” (Trochim & Donnelly, 2008, p. 187), then the researcher will try a sense of confidence that the study will have internal validity to assess whether or not the treatment caused the hypothesized outcome. Well-c......half of the document......cannot build (Experiment-Resources.com, 2010).Experiments and researchThe measurement of the dependent variable is a significant element in experimental and quasi-experimental studies designs and allows comparison of groups. Both designs can show the likelihood 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 knowledge base of research methods. Mason, OH: Cengage.Writing @ CSU. (2010). Differences between experimental research and quasi-experiment research. Retrieved July 19, 2010, from Writing@CSU: http://writing.colostate.edu/guides/research/experiment/pop3e.cfm