What is the primary purpose of randomization in randomized controlled trials (RCTs)?

The primary purpose of randomization in randomized controlled trials (RCTs) is to balance known and unknown confounders between the different groups or arms of the study by chance. This process helps ensure that any external factors that could influence the outcome are distributed equally across the intervention and control groups. By doing so, randomization minimizes the risk of bias and allows researchers to attribute differences in outcomes directly to the effect of the intervention being tested.

When participants are assigned to groups randomly, it reduces systematic differences that could skew the results. This is crucial for the integrity of the study because it means that the results are more likely to reflect the true efficacy of the treatment rather than being influenced by underlying differences between participants. Consequently, randomization is fundamental in establishing causal relationships and enhancing the validity of the trial's findings.