## Purpose of Randomization in RCTs **Key Point:** Randomization is the cornerstone of RCT design and serves to distribute both known and unknown confounding variables equally between groups, thereby establishing comparability at baseline. ### Mechanism of Action Randomization works by: 1. Breaking the link between prognostic factors and treatment assignment 2. Making treatment groups similar in all characteristics except the intervention received 3. Allowing valid statistical inference about causation **High-Yield:** Randomization controls for **unknown confounders**—a unique advantage over observational studies. This is why RCTs are the gold standard for establishing efficacy. ### What Randomization Does NOT Do | Concept | Addressed by Randomization? | Addressed by | |---------|-------|----------| | Known confounders | ✓ Yes (probabilistically) | Stratification, matching | | Unknown confounders | ✓ Yes (unique feature) | — | | Measurement bias | ✗ No | Blinding, standardized protocols | | Statistical power | ✗ No | Adequate sample size calculation | | Selection bias | ✗ No | Proper allocation concealment | **Clinical Pearl:** Even with perfect randomization, baseline imbalances can occur by chance in small samples—this is why baseline characteristics tables are reported. **Mnemonic: RAC** — **R**andomization addresses **A**ll confounders (known and unknown), **C**reating comparable groups.
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