Power analysis for longitudinal trials

描述（由申请人提供）：纵向试验是研究人员在一段时间内跟踪结果的试验。这些试验在药物滥用、衰老、医学、社会科学和教育等许多领域发挥着重要作用。纵向研究，就其性质而言，往往涉及对长期健康和发展有重要影响的问题。此外，由于这些研究通常被视为决定性的，其结果可能对政策产生重大影响。已经发表了超过50，000项此类研究，近年来这种设计的使用一直在增加。计划和分析纵向试验所需的统计程序比简单随机试验所用的统计程序复杂得多。流行的软件包，如SPSS，SAS和Stata包括用于分析纵向试验的模块，并且绝大多数这些试验都使用这些类型的模块进行分析。相比之下，没有商业软件来计算这些试验的功效，并且在计划这些研究时使用适当的技术来计算功效是极其罕见的。在大多数情况下，研究人员通过忽略研究的纵向方面并使用用于简单随机试验的技术来计算功效。这是一个严重的问题，因为这种方法可能会产生严重错误的功率估计。这个项目的目标是开发软件来计算纵向研究的功率。该程序将与一系列研究设计一起使用，并将包含一个复杂的用户界面，以解决在功效分析中必须解决的各种现实问题。在输入端，它将允许用户输入他们可能拥有的数据类型，并使用清晰直观的界面进行输入。在输出端，程序将创建表格和图形，允许用户快速评估所有假设的影响，并确定设计中的变化将如何影响功率和成本。

DESCRIPTION (provided by applicant): Longitudinal trials are trials in which researchers track outcomes over a period of time. These trials play a prominent role in many fields including drug abuse, aging, medicine, social science, and education. Longitudinal studies, by their nature, often address issues that have important implications for long-term health and development. Also, because these studies are often seen as definitive, their results may have a substantial impact on policy. There have been more than 50,000 of these studies published, and the use of this design has been increasing in recent years. The statistical procedures required to plan and to analyze a longitudinal trial are substantially more complex than those used for simple randomized trials. Popular software packages such as SPSS, SAS, and Stata include modules for the analysis of longitudinal trials, and the vast majority of these trials are analyzed using these kinds of modules. By contrast, there is no commercial software to compute power for these trials, and the use of proper techniques to compute power when these studies are being planned is extremely rare. In most cases researchers compute power by ignoring the longitudinal aspect of the study and using techniques intended for simple randomized trials. This is a serious problem because this approach can yield estimates of power that are substantially in error. The goal of this project is to develop software to compute power for longitudinal studies. The program will work with an array of study designs, and it will incorporate a sophisticated user interface to address the kinds of real-world issues that must be addressed in a power analysis. On the input side, it will allow users to enter the kinds of data that they are likely to have, and to do so using a clear and intuitive interface. On the output side the program will create tables and graphs that allow the user to quickly assess the impact of all assumptions, and to determine how changes in the design would affect power and costs.