What is a characteristic of an event referred to as 'history' in research?

In research, 'history' refers to external events that occur during the course of a study, which can impact the outcomes and the validity of the results. This characteristic signifies that while a study might be designed carefully to measure specific variables, unforeseen external events can influence both the experimental group and control group similarly, potentially skewing the results.

For instance, if a significant social event or natural disaster happens while a study is underway, it might affect participants' behaviors or responses in both groups, making it difficult to attribute changes solely to the variables being tested. This understanding of history as an external factor underscores the importance of controlling for such events in research design to enhance the internal validity of the study's findings.