Psychology: Human Services

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Internal validity in experimental research refers to the accuracy of a study and how well the research can conclude that the dependent variable arose only from the independent variable. It tends to answer the question whether the treatment done by the researcher caused a change subject’s behavior other than from other factors. In the descriptive researchers, internal validity refers to the quality of the study. External validity is the ability of results from a study to have generalizations or applications to other settings (Slack & Draugalis, 2001). Group research work that uses randomization has a higher external validity than those that do not use a random selection.
When conducting research, there is a trade-off between internal and external validity. It is because confounds threaten internal validity and artifacts threaten external validity. Confounds influence the dependent variable and vary systematically with the independent variable. Artifacts remain constant in a study but influence the relation between the variables. A highly controlled experimental design eliminates confounds. On the other hand, a less ...
... controlled experiment is subject to many confounding variables (Jimenez-Buedo & Miller, 2010).
Randomization and use of research design help to achieve high internal and external validity. The statistical analysis used should be appropriate to the type of data (Davis-Becker & Buckendahl, 2013). The case studies experiments have a high internal validity since the subjects serve particular controls but are low in relation to external validity. The method used to achieve a high external validity in the case study experiments is replication and extension processes. A high internal validity helps the researcher get stronger deductions relating to the causal impacts of the independent variable. On the other hand, increasing external validity allows extraneous variables into the research.
An attempt to increase both internal and external validity may not be easy since the two have an inverse relationship. However, having a balance to both of them ensures that the results are not only viable but can have generalizations beyond the study.

References
Campbell, D. T., & Stanley, J. C. (1966) Experimental and quasi-experimental designs for research Chicago: Rand McNally.

Davis-Becker, S. L., & Buckendahl, C. W. (2013) Identifying and Evaluating External Validity Evidence for Passing Scores: International Journal of Testing, 13(1), 50-64.

Isaac, S., & Michael, W. B. (1971) Handbook in research and evaluation, San Diego

Jimenez-Buedo, M., & Miller, L. (2010) Why a Trade-Off? The Relationship between the External and Internal Validity of Experiments: An International Journal for Theory, History And Foundations Of Science, 25(3), 301-321.

Slack MK, Draugalis (2001) Establishing the Internal and External validity of experimental studies: JR. Am J Health Syst Pharm 58(22):2173-81; quiz 2182-3

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