In a study designed to determine whether a treatment causes an outcome, which concept guards against confounding?

• A. Internal Validity
• B. External Validity
• C. Causal Inference
• D. Hypothesis

Answer: (A)

Internal validity is about whether the study design and execution ensure that the observed treatment-outcome relationship really reflects a causal effect within the study, free from alternative explanations caused by confounding. Confounding occurs when another variable is linked to both the treatment and the outcome, creating a misleading impression of causality. Methods like randomization, proper control groups, blinding, and careful measurement help balance or eliminate those alternative explanations, so the outcome can be attributed to the treatment itself.

External validity concerns whether these findings generalize to other populations or settings, not whether confounding was controlled in the study. Causal inference is the broader process of reasoning about cause-and-effect, which relies on strong internal validity to make credible claims. A hypothesis is simply a proposed statement to be tested, not a mechanism for guarding against confounding.