中文摘要：

目的探讨生存分析log-rank检验样本含量估计的影响因素。方法应用PASS软件中的Lachin-Foulkes方法模块,设置不同的参数计算实例的样本含量来研究log-rank检验样本含量估计的影响因素。结果检验水准（包括单、双侧检验）、预期的检验效能、风险比、试验组和对照组例数是否均衡、随访的时间、删失率等因素都会影响log-rank检验样本含量估计。结论生存分析log-rank检验样本含量估计受诸多因素影响,设计阶段样本含量估算应考虑这些影响因素。

英文摘要：

ObjectiveTo discuss contributing factors of sample size evaluation for log-rank test in survival analysis. MethodsBased on Lachin-Foulke module of PASS,different parameters were set to compute sample sizes for an example to explore factors of sample size evaluation for log-rank test. ResultsSignificance level（one-sided or two-sided）,power,hazard ratio,sample distribution of two groups,follow time,and censored percent will influence sample size estimation for log-rank test. ConclusionSeveral factors determined sample size evaluation for log-rank test and should be considered during experimental design.