The advantages of an experimental research design in psychological research include the ability to test causal relationships and the ability to control variables. The disadvantages of experimental research include external validity and artificial situations.
Experimental design is the only research design that allows for causal testing. All other research is limited to testing correlations. In psychology examining cause-and-effect relationships allows researchers to understand how independent variables impact dependent variables. The ability of a researcher to control variables is also important because experiments can be constructed to isolate any given independent variables. This allows researchers to perform experiments they are not able to conduct in a real-world situation.
The artificiality of experiments, however, is a major limitation of the method. While researchers can isolate any variable, results may not be generalized outside of the given context in which the research occurred. External validity, which occurs when the results of a research study are applicable to situations outside of the study, can be low in experimental research.
Sampling becomes very important to improve generalizability. A researcher must sample a group of people that represents the population being studied. Simple random sampling, which is a random selection of individuals from a given population, can be used to ensure that bias is reduced in experiments.