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Precise and accurate power of the rank-sum test for a continuous outcome.
Journal of Biopharmaceutical Statistics ( IF 1.2 ) Pub Date : 2020-03-04 , DOI: 10.1080/10543406.2020.1730866
Katie R Mollan 1 , Ilana M Trumble 1 , Sarah A Reifeis 1 , Orlando Ferrer 1 , Camden P Bay 1 , Pedro L Baldoni 1 , Michael G Hudgens 1
Affiliation  

Accurate power calculations are essential in small studies containing expensive experimental units or high-stakes exposures. Herein, power of the Wilcoxon Mann–Whitney rank-sum test of a continuous outcome is formulated using a Monte Carlo approach and defining P ( X < Y ) p as a measure of effect size, where X and Y denote random observations from two distributions hypothesized to be equal under the null. Effect size p fosters productive communications because researchers understand p = 0.5 is analogous to a fair coin toss, and p near 0 or 1 represents a large effect. This approach is feasible even without background data. Simulations were conducted comparing the empirical power approach to existing approaches by Rosner & Glynn, Shieh and colleagues, Noether, and O’Brien-Castelloe. Approximations by Noether and O’Brien-Castelloe are shown to be inaccurate for small sample sizes. The Rosner & Glynn and Shieh, Jan & Randles approaches performed well in many small sample scenarios, though both are restricted to location-shift alternatives and neither approach is theoretically justified for small samples. The empirical method is recommended and available in the R package wmwpow.



中文翻译:

秩和检验对连续结果的精确和准确的功效。

在包含昂贵的实验单元或高风险暴露的小型研究中,准确的功率计算是必不可少的。在此,连续结果的 Wilcoxon Mann-Whitney 秩和检验的功效是使用蒙特卡罗方法制定的,并定义 ( X < ) 作为效应大小的度量,其中 X 表示假设在零下相等的两个分布的随机观察。规模效应 促进富有成效的交流,因为研究人员了解 = 0.5 类似于一次公平的抛硬币,并且 接近 0 或 1 表示效果很大。即使没有背景数据,这种方法也是可行的。Rosner & Glynn、Shieh 及其同事、Noether 和 O'Brien-Castelloe 进行了模拟,将经验功效方法与现有方法进行了比较。Noether 和 O'Brien-Castelloe 的近似值被证明对于小样本量是不准确的。Rosner & Glynn 和 Shieh、Jan & Randles 方法在许多小样本场景中表现良好,尽管两者都仅限于位置偏移替代方案,而且这两种方法在理论上都不适用于小样本。R 包 wmwpow 中推荐并提供了经验方法。

更新日期:2020-03-04
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