What does randomization achieve in experimental studies?

• A. Eliminates all bias
• B. Guarantees causality
• C. Increases sample size automatically
• D. Reduces confounding due to measured/unmeasured variables

Answer: (D)

Randomization assigns participants to groups by chance, which helps balance both known and unknown factors that could influence the outcome. By distributing these potential confounders evenly across groups, any differences observed in outcome are more likely due to the intervention itself rather than preexisting differences. This reduction in confounding applies to both measured and unmeasured variables, which is why randomization is so powerful in experimental studies. It doesn’t guarantee that all bias is gone, and it doesn’t by itself establish causality or change the study’s sample size.