Are Power Analyses Reported With Adequate Detail? Evidence From the First Wave of Group Randomized Trials Funded by the Institute of Education Sciences

Abstract

This study examines the reporting of power analyses in the group randomized trials funded by the Institute of Education Sciences from 2002 to 2006. A detailed power analysis provides critical information that allows reviewers to (a) replicate the power analysis and (b) assess whether the parameters used in the power analysis are reasonable. Without a detailed power analysis, reviewers may have difficultly evaluating the accuracy of the power analysis and underpowered studies may inadvertently pass through the review process with a recommendation for funding. This study reveals that sample sizes are reported with high consistency; however, other important design parameters, including intraclass correlations, covariate-outcome correlations, and the percentage of variance explained by blocking are not reported with regularity. An analysis of reporting trends over time reveals that the reporting of intraclass correlations and covariate-outcome correlations dramatically increased over time. The reporting of blocking information was still extremely limited, even in the more recent studies.     

PowerUp!: A Tool for Calculating Minimum Detectable Effect Sizes and Minimum Required Sample Sizes for Experimental and Quasi-Experimental Design Studies

Abstract

This paper and the accompanying tool are intended to complement existing supports for conducting power analysis tools by offering a tool based on the framework of Minimum Detectable Effect Sizes (MDES) formulae that can be used in determining sample size requirements and in estimating minimum detectable effect sizes for a range of individual- and group-random assignment design studies and for common quasi-experimental design studies. The paper and accompanying tool cover computation of minimum detectable effect sizes under the following study designs: individual random assignment designs, hierarchical random assignment designs (2-4 levels), block random assignment designs (2-4 levels), regression discontinuity designs (6 types), and short interrupted time-series designs. In each case, the discussion and accompanying tool consider the key factors associated with statistical power and minimum detectable effect sizes, including the level at which treatment occurs and the statistical models (e.g., fixed effect and random effect) used in the analysis. The tool also includes a module that estimates for one and two level random assignment design studies the minimum sample sizes required in order for studies to attain user-defined minimum detectable effect sizes.     

How Much Do the Effects of Education and Training Programs Vary Across Sites? Evidence From Past Multisite Randomized Trials

Multisite trials, in which individuals are randomly assigned to alternative treatment arms within sites, offer an excellent opportunity to estimate the cross-site average effect of treatment assignment (intent to treat or ITT) and the amount by which this impact varies across sites. Although both of these statistics are substantively and methodologically important, only the first has been well studied. To help fill this information gap, we estimate the cross-site standard deviation of ITT effects for a broad range of education and workforce development interventions using data from 16 large multisite randomized controlled trials. We use these findings to explore hypotheses about factors that predict the magnitude of cross-site impact variation, and we consider the implications of this variation for the statistical precision of multisite trials.     

不同家庭结构下的传递不平衡检验的功效(英文)

近年来 ,连锁和关联分析最流行的方法要属传递不平衡检验 (TDT) 而评估TDT的功效和样本大小至关重要 许多文章已讨论此问题 但以前的方法既不精确也不一般化 他们都作了一个简单的假设 ,即每个家庭仅有一个受累子代或两个受累同胞对或非受累同胞对 一个例外是Chen和Deng发展的方法 但他们并没有考虑不同比例的这些家庭对TDT功效和样本大小的影响 本文应用“PC”软件 ,调查了在四个遗传模式下不同的家庭结构对TDT功效的影响 ,考虑以下三种情形 :(1)不同家庭结构的不同比例 ,(2 )标记和易感基因间的不同重组率 ,(3)父母的不同致病状态 调查具有实践意义 因为在实际中 ,更多的是征集到不同结构的家庭 如何设计不同家庭的比例相当重要     

Introducing the mean absolute deviation ‘effect’ size

This paper revisits the use of effect sizes in the analysis of experimental and similar results, and reminds readers of the relative advantages of the mean absolute deviation as a measure of variation, as opposed to the more complex standard deviation. The mean absolute deviation is easier to use and understand, and more tolerant of extreme values. The paper then proposes the use of an easy to comprehend effect size based on the mean difference between treatment groups, divided by the mean absolute deviation of all scores. Using a simulation based on 1656 randomised controlled trials each with 100 cases, and a before and after design, the paper shows that the substantive findings from any such trial would be the same whether raw-score differences, a traditional effect size like Cohen's d, or the mean absolute deviation effect size is used. The same would be true for any comparison, whether for a trial or a simpler cross-sectional design. It seems that there is a clear choice over which effect size to use. The main advantage in using raw scores as an outcome measure is that they are easy to comprehend. However, they might be misleading and so perhaps require more judgement to interpret than traditional ‘effect’ sizes. Among the advantages of using the mean absolute deviation effect size are its relative simplicity, everyday meaning, and the lack of distortion of extreme scores caused by the squaring involved in computing the standard deviation. Given that working with absolute values is no longer the barrier to computation that it apparently was before the advent of digital calculators, there is a clear place for the mean absolute deviation effect size (termed ‘A’).     

对相干态的非线性高阶压缩效应

研究了对相干态|ζ>=A0n=∞∑0nnζ!|n,n>的非线性高阶压缩效应.结果表明:对于对相干态,光场存在着等阶N(=2,3,4,5,…)次方Y压缩效应,但不存在着等阶N次方H压缩效应,对相干态是N-H最小不确定态.     

“不客气”和“别客气”

对“不客气”和“别客气”进行多方面比较的结果表明：“不客气”和“别客气”在使用语境、词语增量和语法单位上存在差异;在语用上,“不客气”比“别客气”更礼貌。其深层理据在于：第一,“不客气”的主语是言者主语,“别客气”的主语是句子主语,而二者主语的分别是移情策略在言语交际中的运用;第二,语法化对语义的制约,“不客气”的语法意义是不必要客气,“别客气”的语法意义是不需要客气,“不客气”强调客观不必要,自然更易为听话人接受。     

Effects of rarefaction on the characteristics of micro gas journal bearings

Given the definition of the reference Knudsen number for micro gas journal bearings, the range in the number is related to the viscosity of air at different temperatures. A modified Reynolds equation for micro gas journal bearings based on Burgdorfer＇s first-order slip boundary condition is proposed that takes into account the gas rarefaction effect. The finite difference method （FDM） is adopted to solve the modified Reynolds equation to obtain the pressure profiles, load capacities and attitude angles for micro gas journal bearings at different reference K_nudsen numbers, bearing numbers and journal eccentricity ratios. Numerical analysis shows that pressure profiles and non-dimensional load capacities decrease markedly as gas rarefaction increases. Attitude angles change conversely, and when the eccentricity ratio is less than 0.6, the attitude angles rise slightly and the influence of the reference Knudsen number is not marked. In addition, the effect of gas rarefaction on the non-dimensional load capacity and attitude angle decreases with smaller bearing numbers.     

Allocating Sample Sizes to Reduce Budget for Fixed-Effect 2×2 Heterogeneous Analysis of Variance

This article discusses the sample size requirements for the interaction, row, and column effects, respectively, by forming a linear contrast for a 2×2 factorial design for fixed-effects heterogeneous analysis of variance. The proposed method uses the Welch t test and its corresponding degrees of freedom to calculate the final sample size in a 2-step procedure. The simulation results show that the proposed sample size allocation ratio can minimize the sampling cost, while at the same time the designated power is achieved. The article concludes with a discussion to reiterate the importance of sample size planning, especially for testing the iteration effect.     

社会认知视野的自我参照效应相对性哲学辨析

通过对自我参照效应相关研究的分析和总结,探讨了个体、群体、本体自我三个层面的自我参照效应,包括自我参照效应的概念、研究范式、研究对象等.进而从对立统一规律的视角归纳出自我参照效应的相对性,指出了自我参照效应研究中的不足及其展望.