Zhang Song, Cao Jing, Ahn Chul
Department of Clinical Sciences, UT Southwestern Medical Center, Dallas, TX, United States.
Department of Statistical Science, Southern Methodist University, Dallas, TX, United States.
Contemp Clin Trials. 2018 Jan;64:274-280. doi: 10.1016/j.cct.2015.09.015. Epub 2015 Sep 28.
We investigate sample size calculation for before-after experiments where the outcome of interest is binary and the enrolled subjects contribute a mixed type of data: some subjects contribute complete pairs of before- and after-intervention outcomes, while some subjects contribute incomplete data (before-intervention only or after-intervention only). We use the GEE approach to derive a closed-form sample size formula by treating the incomplete observations as missing data in a generalized linear model. The impacts of various designing factors are appropriately accounted for in the sample size formula, including intervention effect, baseline response rate, within-subject correlation, and distribution of missing values in the before- and after-intervention periods. We illustrate sample size estimation using a real application example. We conduct simulation studies to demonstrate that the proposed sample size maintains the nominal power and type I error under a wide spectrum of trial configurations.
我们研究前后对照实验的样本量计算问题，这类实验中感兴趣的结果是二元的，且纳入的受试者贡献了混合类型的数据：一些受试者贡献了干预前后结果的完整配对，而一些受试者贡献了不完整数据（仅干预前或仅干预后）。我们使用广义估计方程（GEE）方法，通过将不完整观测值视为广义线性模型中的缺失数据，推导出一个封闭式样本量公式。样本量公式中适当考虑了各种设计因素的影响，包括干预效果、基线反应率、受试者内相关性以及干预前后时期缺失值的分布。我们用一个实际应用例子来说明样本量估计。我们进行模拟研究以证明所提出的样本量在广泛的试验配置下保持名义检验效能和I型错误。
