Randomization is the key to ensure the balance of confounders between the comparison groups in clinical trials, and it is the statistical basis for making the study results comparable. A simple randomization in a clinical trial with large sample-size allows for a balanced comparison of the number of subjects and confounding factors between groups, but in a clinical trial with small sample-size, it is necessary to use a restricted randomization method (the blocked randomization). Block randomization ensures that the number of subjects between groups is basically equal, maximize the effectiveness of clinical trials as the standard error of the treatment-effect estimate is decreased, which affords big rewards in scientific accuracy and credibility.
随机化是确保临床试验中比较组间混杂因素均衡的关键，是使研究结果具有可比性的统计学基础。在大样本中简单的随机化就可以均衡比较组间受试者的数量和混杂因素，但在小样本中要实现受试者数量组间均衡的目的，需要选择限制性随机化方法中的区组随机化。区组随机化方法通过保证比较组间研究对象数量的基本相等，使临床试验的检验效能最大化，同时降低估计处理效应的标准误差，这对提升随机对照试验研究的准确性和可信度有十分重要的意义。.
Keywords: Block randomization; Clinical trial.