Back to basics: explaining sample size in outcome trials,are statisticians doing a thorough job?

Time to event outcome trials in clinical research are typically large, expensive and high‐profile affairs. Such trials are commonplace in oncology and cardiovascular therapeutic areas but are also seen in other areas such as respiratory in indications like chronic obstructive pulmonary disease. Their progress is closely monitored and results are often eagerly awaited. Once available, the top line result is often big news, at least within the therapeutic area in which it was conducted, and the data are subsequently fully scrutinized in a series of high‐profile publications. In such circumstances, the statistician has a vital role to play in the design, conduct, analysis and reporting of the trial. In particular, in drug development it is incumbent on the statistician to ensure at the outset that the sizing of the trial is fully appreciated by their medical, and other non‐statistical, drug development team colleagues and that the risk of delivering a statistically significant but clinically unpersuasive result is minimized. The statistician also has a key role in advising the team when, early in the life of an outcomes trial, a lower than anticipated event rate appears to be emerging. This paper highlights some of the important features relating to outcome trial sample sizing and makes a number of simple recommendations aimed at ensuring a better, common understanding of the interplay between sample size and power and the final result required to provide a statistically positive and clinically persuasive outcome. Copyright © 2009 John Wiley & Sons, Ltd.     

二元对立在《远大前程》中的体现

探讨《远大前程》中的三组主要的二元对立,分析作者对人性本真的肯定和对不切实际的幻想的否定,同时也通过二元对立的分析揭示了大英帝国的罪恶和对海外殖民地的掠夺的事实。     

A simple approach for generating correlated binary variates ∗

Correlated binary data arise frequently in medical as well as other scientific disciplines; and statistical methods, such as generalized estimating equation (GEE), have been widely used for their analysis. The need for simulating correlated binary variates arises for evaluating small sample properties of the GEE estimators when modeling such data. Also, one might generate such data to simulate and study biological phenomena such as tooth decay or periodontal disease. This article introduces a simple method for generating pairs of correlated binary data. A simple algorithm is also provided for generating an arbitrary dimensional random vector of non-negatively correlated binary variates. The method relies on the idea that correlations among the random variables arise as a result of their sharing some common components that induce such correlations. It then uses some properties of the binary variates to represent each variate in terms of these common components in addition to its own elements. Unlike most previous approaches that require solving nonlinear equations or use some distributional properties of other random variables, this method uses only some properties of the binary variate. As no intermediate random variables are required for generating the binary variates, the proposed method is shown to be faster than the other methods. To verify this claim, we compare the computational efficiency of the proposed method with those of other procedures.     

用于QR码自动识读的图像分析方法

对于所采集的条码图像,为了适应实时性的要求,以得到不同光照条件下的最佳阈值,该文提出了把直方图双峰法、OTSU法及NLNiblack阈值法结合起来的改进的自适应阈值法。实验证明了该方法具有高效性和稳定性。为了在条码分割图像中获取QR码的4个顶点,首先,根据3个位置探测图形的特性提出了一种新的方法以求取对应的3个顶点,同时利用QR码的特征提出挖空算法获取条码的边缘,再采用过已知点的Hough变换得到第4个顶点。实验证明该算法在各种采集条件下可有效地得到QR码的4个顶点。     

聚合物/表面活性剂二元复合驱研究进展

从聚合物/表面活性剂二元体系的特点出发，综述了聚/表聚/表二元复合体系的实验室研究现状以及在胜利油田孤东七区54-61进行的矿场试验情况。聚/表二元复合驱是在聚/表/碱三元复合驱的基础上去掉碱所形成的低浓度的驱油体系，可以最大限度地发挥聚合物的粘度和弹性，减少乳化液处理带来的负面影响，减弱由于碱的存在引起的地层以及井筒结垢的现象。通过国内外研究结果分析表明，聚/表二元复合体系提高原油采收率幅度在20%左右；矿场试验取得了较好的效果。聚/表二元复合体系可以克服三元体系的缺点，作为一项新的驱油方法具有宽阔的发展空间。     

Assessing Effects on Long-term Survival after Early Termination of Randomized Trials

In this paper we present an approach to using historical control data to augment information from a randomized controlled clinical trial, when it is not possible to continue the control regimen to obtain the most reliable and valid assessment of long term treatment effects. Using an adjustment procedure to the historical control data, we investigate a method of estimating the long term survival function for the clinical trial control group and for evaluating the long term treatment effect. The suggested method is simple to interpret, and particularly motivated in clinical trial settings when ethical considerations preclude the long term follow-up of placebo controls. A simulation study reveals that the bias in parameter estimates that arises in the setting of group sequential monitoring will be attenuated when long term historical control information is used in the proposed manner. Data from the first and second National Wilms' Tumor studies are used to illustrate the method.     

结构主义文学批评与二项对立

二项对立是结构主义分析中最重要的关系和最基本的方法 ,它在结构主义文学理论中是个重要概念 ,它被广泛应用于结构主义人类学、结构主义诗学和结构主义叙事学。     

一种高性能目标识别融合算法

考虑到目标类型数和传感器扫描次数对识别的影响，提出了一种改进的多传感器多目标识别相关算法，导出了新的累积融合公式。对多传感器多目标识别融合作了计算机模拟，模拟结果证实了改进的算法在性能上有明显的提高。     

Sequential experimental design and response optimisation

We consider the situation where one wants to maximise a functionf(θ,x) with respect tox, with θ unknown and estimated from observationsy _k . This may correspond to the case of a regression model, where one observesy _k =f(θ,x _k )+ε _k , with ε _k some random error, or to the Bernoulli case wherey _k ∈{0, 1}, with Pr[y _k =1|θ,x _k |=f(θ,x _k ). Special attention is given to sequences given by , with an estimated value of θ obtained from (x₁, y₁),...,(x _k ,y _k ) andd _k (x) a penalty for poor estimation. Approximately optimal rules are suggested in the linear regression case with a finite horizon, where one wants to maximize ∑ _i=1 ^N w _i f(θ, x _i ) with {w _i } a weighting sequence. Various examples are presented, with a comparison with a Polya urn design and an up-and-down method for a binary response problem.     

非单调二元非线性算子方程组的迭代求解

利用锥与半序理论和混合单调算子理论 ,讨论 Banach空间中非单调二元非线性算子方程组解的存在性与唯一性 ,并给出收敛于方程组解的迭代序列和误差估计 ,改进和推广了混合单调算子方程和一元算子方程的某些相应结果 .