Randomized Field Trials and Internal Validity: Not So Fast My Friend. - Practical Assessment, Research & Evaluation

The purpose of this article is to summarize eight potential threats to internal validity that occur with randomized field trial (RFT) studies. Depending on specific contextual factors, RFTs do not necessarily result in strong internal validity. Of particular concern is whether the unit of random assignment is the same as the number of replications of the intervention, threats as a result of local history, and subject effects. The eight threats are described, with suggestions for providing adequate monitoring to know if they rise to the level of likely or plausible threat to internal validity.