Final answer:
Internal validity refers to the extent to which an experiment convincingly shows that changes in behavior are caused by the independent variable and not other variables.
Step-by-step explanation:
The extent to which an experiment shows convincingly that changes in behavior are a function of the independent variable (IV) and not the result of uncontrolled or unknown variables is called internal validity.
Internal validity is important in experimental research because it ensures that the independent variable is truly responsible for the changes in behavior that are observed. To establish internal validity, experiments must be designed to control for extraneous variables and minimize bias. This can be achieved through random assignment, using control groups, and implementing placebo treatments.
For example, in a study examining the effect of a new medication on behavior, participants would be randomly assigned to either the experimental group, which receives the medication, or the control group, which receives a placebo. By using random assignment and a control group, researchers can be more confident that any differences in behavior are due to the medication and not other factors.