If an intervention is hoped to reduce mortality (ie, the endpoint is overall survival) from 30% to 15%, the risk ratio is 2, with a binomial sample size calculation of 320.

• 如果介入是有望于将死亡率（例，终点是总存活数）从30%25减小至15%25，风险比率是2，采用320的二项式样本量计算