Which extent term describes the extent to which an experiment shows that changes are due to the independent variable and not to other variables?

• A. Voluntariness
• B. Capacity
• C. Information
• D. Internal Validity

Answer: (D)

The main idea here is whether a study demonstrates that observed changes come from the manipulated variable rather than from other factors. Internal validity measures how confident we can be that the independent variable caused the effect, not some confounding factor. When a design has high internal validity, you’ve controlled potential alternatives—like differences in who’s in each group, or other variables that could influence the outcome—so the experiment can support a causal claim that the IV is responsible for the changes seen in the dependent variable. Strengthening internal validity involves using proper control conditions, random assignment when possible, keeping procedures consistent across conditions, and monitoring or controlling potential confounds.

The other terms aren’t about causal attribution in experiments. Voluntariness relates to whether participants freely choose to participate, and capacity concerns whether they have the ability to consent. Information typically touches on what participants are told or what is recorded, not on whether the IV caused the observed effect.