Simulation-based power calculation for designing interrupted time series analyses of health policy interventions
Simulation-based power calculation for designing interrupted time series analyses of health policy interventions
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DOI：
10.1016/j.jclinepi.2011.02.007
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发表时间：
2011-11-01
影响因子：
7.2
通讯作者：
Ross-Degnan, Dennis
中科院分区：
文献类型：
--
作者：
Zhang, Fang;Wagner, Anita K.;Ross-Degnan, Dennis
目的：中断时间序列是一种强有力的准实验研究设计，用于评估卫生政策干预的影响。利用仿真方法，我们估计了中断时间序列研究在不同情况下的功率需求。研究设计和设置：进行模拟，以估计自相关范围为-0.9至0.9，效应大小为0.5,1.0和2.0时分割自回归（AR）误差模型的功率，调查干预前后平衡和不平衡时间段的数量。本文还探讨了自回归条件异方差（ARCH）模型的简单场景。结果：AR模型的功率随样本量或效应量的增加而增加，随自相关的增加而降低。与干预前后研究周期数量平衡的设计相比，周期数量不平衡的设计具有更低的功率，尽管ARCH模型并非如此。结论：对于许多实际应用来说，检测效应大小1.0的能力似乎是合理的，在研究中，中等或大量的时间点平均分布在干预周围。当预期效应量较小或时间点数量较少时，研究者应谨慎。我们建议在调查前进行各种模拟。(C) 2011爱思唯尔公司版权所有。
Objective: Interrupted time series is a strong quasi-experimental research design to evaluate the impacts of health policy interventions. Using simulation methods, we estimated the power requirements for interrupted time series studies under various scenarios.Study Design and Setting: Simulations were conducted to estimate the power of segmented autoregressive (AR) error models when autocorrelation ranged from -0.9 to 0.9 and effect size was 0.5, 1.0, and 2.0, investigating balanced and unbalanced numbers of time periods before and after an intervention. Simple scenarios of autoregressive conditional heteroskedasticity (ARCH) models were also explored.Results: For AR models, power increased when sample size or effect size increased, and tended to decrease when autocorrelation increased. Compared with a balanced number of study periods before and after an intervention, designs with unbalanced numbers of periods had less power, although that was not the case for ARCH models.Conclusion: The power to detect effect size 1.0 appeared to be reasonable for many practical applications with a moderate or large number of time points in the study equally divided around the intervention. Investigators should be cautious when the expected effect size is small or the number of time points is small. We recommend conducting various simulations before investigation. (C) 2011 Elsevier Inc. All rights reserved.