Sample size can be a key design feature that not only affects the probability of a trial＇s success but also determines the duration and feasibility of a trial. If an investigational drug is expected to be effective a...Sample size can be a key design feature that not only affects the probability of a trial＇s success but also determines the duration and feasibility of a trial. If an investigational drug is expected to be effective and address unmet medical needs of an orphan disease, where the accrual period may require many years with a large sample size to detect a minimal clinically relevant treatment effect, a minimum sample size may be set to maintain nominal power. In limited situations such as this, there may be a need for flexibility in the initial and final sample sizes; thus, it is useful to consider the utility of adaptive sample size designs that use sample size re-estimation or group sequential design. In this paper, we propose a new adaptive performance measure to consider the utility of an adaptive sample size design in a trial simulation. Considering that previously proposed sample size re-estimation methods do not take into account errors in estimation based on interim results, we propose Bayesian sample size re-estimation criteria that take into account prior information on treatment effect, and then, we assess its operating characteristics in a simulation study. We also present a review example of sample size re-estimation mainly based on published paper and review report in Pharmaceuticals and Medical Devices Agency （PMDA）.展开更多
For costly and/or destructive tests,the sequential method with a proper maximum sample size is needed.Based on Koopman-Darmois distributions,this paper proposes the method of sequential mesh,which has an acceptable ma...For costly and/or destructive tests,the sequential method with a proper maximum sample size is needed.Based on Koopman-Darmois distributions,this paper proposes the method of sequential mesh,which has an acceptable maximum sample size.In comparison with the popular truncated sequential probability ratio test,our method has the advantage of a smaller maximum sample size and is especially applicable for costly and/or destructive tests.展开更多
文章选取车架生产中主要不确定量热轧钢板厚度为随机设计变量,基于Hammersly采样法对40t重型车主要承载构件车架进行静态强度、刚度和动态振动特性的多学科可靠性计算分析;结合多学科和可靠性优化理论,采用基于自适应面的SORA(sequentia...文章选取车架生产中主要不确定量热轧钢板厚度为随机设计变量,基于Hammersly采样法对40t重型车主要承载构件车架进行静态强度、刚度和动态振动特性的多学科可靠性计算分析;结合多学科和可靠性优化理论,采用基于自适应面的SORA(sequential optimization and reliability assessment)可靠性单层循环优化方法对该车架进行基于可靠性的多学科优化设计,使得可靠度由原设计方案的50%左右提高到95%、车架质量减少2.3%。展开更多
文摘Sample size can be a key design feature that not only affects the probability of a trial＇s success but also determines the duration and feasibility of a trial. If an investigational drug is expected to be effective and address unmet medical needs of an orphan disease, where the accrual period may require many years with a large sample size to detect a minimal clinically relevant treatment effect, a minimum sample size may be set to maintain nominal power. In limited situations such as this, there may be a need for flexibility in the initial and final sample sizes; thus, it is useful to consider the utility of adaptive sample size designs that use sample size re-estimation or group sequential design. In this paper, we propose a new adaptive performance measure to consider the utility of an adaptive sample size design in a trial simulation. Considering that previously proposed sample size re-estimation methods do not take into account errors in estimation based on interim results, we propose Bayesian sample size re-estimation criteria that take into account prior information on treatment effect, and then, we assess its operating characteristics in a simulation study. We also present a review example of sample size re-estimation mainly based on published paper and review report in Pharmaceuticals and Medical Devices Agency （PMDA）.
文摘For costly and/or destructive tests,the sequential method with a proper maximum sample size is needed.Based on Koopman-Darmois distributions,this paper proposes the method of sequential mesh,which has an acceptable maximum sample size.In comparison with the popular truncated sequential probability ratio test,our method has the advantage of a smaller maximum sample size and is especially applicable for costly and/or destructive tests.
文摘文章选取车架生产中主要不确定量热轧钢板厚度为随机设计变量,基于Hammersly采样法对40t重型车主要承载构件车架进行静态强度、刚度和动态振动特性的多学科可靠性计算分析;结合多学科和可靠性优化理论,采用基于自适应面的SORA(sequential optimization and reliability assessment)可靠性单层循环优化方法对该车架进行基于可靠性的多学科优化设计,使得可靠度由原设计方案的50%左右提高到95%、车架质量减少2.3%。
