What is History?
- Content Type:
- Glossary
History Definition
Things that happen or outside variables that change between the beginning and end of an experiment. See also maturation.
In experimental research, history refers to external events or variables that occur between the beginning and end of an experiment and that may influence participants’ responses or outcomes. These changes are unrelated to the experimental treatment itself but can affect the results - potentially confounding the researcher’s ability to attribute observed effects to the independent variable.
What is an example of a history effect in a marketing research experiment?
Imagine a company testing the effectiveness of a new television advertisement for a household cleaning product over a four-week period. Halfway through the study, a widely publicized news story breaks about chemical safety concerns in cleaning products. As a result, consumers in the experiment may become more cautious or skeptical about all cleaning brands.
Even though the company’s ad itself didn’t cause this shift in attitude, the external event (the news coverage) influenced participants’ perceptions and responses. This outside influence is known as a history effect. It introduces a threat to the experiment’s internal validity, because it becomes unclear whether changes in brand perception were due to the new advertisement or the unrelated external event.
In marketing research, recognizing and controlling for history effects is critical when experiments span multiple days or weeks, since real-world factors can unintentionally alter outcomes.