Monday, August 10, 2015

Threats to Internal and External Validity....Industrial Organizational Psychology College Submission by Sean Delevan

Threats to Internal and External Validity
Sean Delevan
31 July 2015

            Validity refers to the degree in which accurate assumptions can be made merely by the results of a research study. Internal validity is described as “validity of the inference that the independent and dependent variables are causally related” (Christensen et al, 2011, pg.2/25). Comparatively, external validity is explained to be the determination regarding whether the “causal relationship holds over people, settings, treatment variable, measurement variables, and time” (Christensen et al, 2011, pg.3/25). Although each are present in research and are necessary to ensure reliability and validity are achieved, there are annotatable threats associated with both internal and external validity that have to be considered during the research process. The purpose of this assignment is to present, in the information to follow, a chart that serves as a master list of threats associated with both internal and external validity in research.
Internal Validity- “How well and experiment is done and if it avoids confounding variables” (Campbell, 1986).
External Validity- “validity of generalized inferences in research based on experiments” (Calder, Phillips, & Tybout, 1982). The extent to which results can be generalized to apply to others.
Threat 1: History – Any past event that can produce the outcome during a study prior to post testing of the dependent variable. “history threat exists in this one-group design if an event occurs (other than the treatment) that can affect the dependent variable” (Christensen et al. 2011). This includes differential history which occurs when one group experiences the changes of the history event but the other group in the study does not.
Threat 1: Population Validity- A testing sample may not actually represent that larger population similar to research participants. The accessible population may be substantially lower than the target population which will skew testing results.
Threat 2: Maturation- Changes in internal conditions such as “age, learning, hunger, boredom, and hunger that are not related to specific external events” (Christensen et al. 2011). Maturation changes are associated with the individual and are realized as biological and/or psychological processes that unwittingly change the outcome of the research.
Threat 2: Ecological Validity- “The generalizability of results of a study across different settings or from one set of environmental conditions to another” (Christensen et al., 2011, pg18/25). Lab experiments don’t generally produce a generalized assumptions for non-lab settings.
Threat 3: Instrumentation- “Changes that occur over time, during the course of the study, in the measurement of the dependent variable” (Christensen et al., 2011, pg.12/25). Research that requires human observance is most likely to suffer from this type of threat.
Threat 3: Temporal Validity- Testing results’ ability to be generalized across an extended period of time. Simply stated, this is a threat if the findings of the study are not held as true over an extended period of time.
Threat 4: Testing- Taking similar tests more than once can change the overall outcome as participants become more familiar with the process. Repetitive tests can desensitize participants and alter the genuine outcome, thus resulting in unreliable results.
Threat 4: Treatment Variation Validity- When the generalizability of study results vary due to different testing administrators. One administrator might be more apt to help participants than another which then changes the reliability and validity of the study altogether.
Threat 5: Regression- Tendency of extreme scores to regress toward a more average score during retesting. When initial tests generate poor results, retaking the same test would expect participants to score higher.
Threat 5: Outcome Validity- “Refers to the generalizability of results across different but related dependent variables” (Christensen et al., 2011, pg.19/25). This measures the same effect that an independent variable has on various dependent variables.
Threat 6: Attrition- This occurs when participants drop out of a study. “Some individuals do not complete a research study for a variety of reasons, such as failure to show up at the scheduled time and place or not participating in all phases of the study” (Christensen et al., 2011, pg.14/25). This is most common in psychological and behavioral studies.

Threat 7: Selection- This threat is present when a differential selection procedure is used for placing participants in certain study groups. Groups in a study might possess different characteristics such as age, ability, or gender, that might affect the results.

Campbell, D. T. (1986). Relabeling internal and external validity for applied social scientists. New Directions for Program Evaluation, 1986(31), 67-77.
Calder, B. J., Phillips, L. W., & Tybout, A. M. (1982). The concept of external validity. Journal of Consumer Research, 240-244.
Christensen, R., Burke, J., & Turner, L. (2011). Research methods, design, and analysis, Eleventh Edition. Pearson Education.

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