纵向研究中的设计问题。

Christopher H Morrell, Veena Shetty, Edward G Lakatta
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引用次数: 0

摘要

在设计纵向研究时,需要决定两个关键组成部分:研究持续时间和访问频率。此外,还必须解决涉及样本量、功率、每个受试者观察次数的其他问题。如果研究要在一定的时间范围内完成,观察之间最好有一个固定的时间(如果达到目标,这可能会使研究提前终止),还是将观察分散在整个研究期间?在研究过程中的某个时刻,可能有兴趣看看额外的数据点是否会有实质性的贡献。假设纵向数据将使用线性混合效应模型进行分析。在这项研究中,我们使用模型参数估计的标准误差作为标准。我们寻求用三种方法来解决这些问题。首先,以多种方式构造数据集的子集,并检查标准误差。其次,使用各种设计,计算固定效应的协方差矩阵,并检查标准误差。最后,进行了仿真研究。
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Design Issues in Longitudinal Studies.

In designing a longitudinal study one needs to decide on two critical components: duration of study and frequency of visits. In addition, other issues involving sample size, power, number of observations per subject must be addressed. If the study is meant to be completed within a certain time frame, would it better to have a fixed time between observations (which might allow the study to terminate early if its objectives are met) or to spread out the observations over the entire study period? At some point during the study, it may be of interest to see if additional data points would contribute substantially. Assume that the longitudinal data will be analyzed using a linear mixed-effects model. In this investigation we use the standard errors of estimates of model parameters as the criterion. We seek to address the issues using three approaches. First, subsets of a data set are constructed in a number of ways and the standard errors are examined. Second, using a variety of designs, the covariance matrix of the fixed-effects is computed and the standard errors are examined. Finally, a simulation study is conducted.

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