What term is used for an external factor that may influence or distort the measurements in a research study?

Answer: Artifacts

Explanation:

Artifacts are the components that are disrupt the external validity or internal validity of result in any research. Artifacts tend to modify or change the authenticity of participant and equipment involved in research field with their presence.

Impact of artifacts can also be influential to understand the process through observing evidences. They impact evidences, documents, tools, equipment, etc.