Answer:
internal validity
Explanation:
Internal validity: The term internal validity refers to the approximate fact of the interference of causal or cause-effect relationships. It is valid in study or research that aims at demonstrating a causal relationship. The internal validity is irrelevant in descriptive and observational studies. It defines the degree to which a given study is being conducted properly.
Threats to internal validity include history, testing, regression instrumentation, selection, or experimental mortality, etc.