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生存数据中组间变异的检验AI 解读

When survival data can be divided into natural groups, such as in a clinical trial with patients from a number of different institutions, the question arises whether effects are different for the different groups. For situations where one is concerned with a random pattern of variation over groups, this article proposes testing the null hypothesis of no variation using statistics based on the sums of martingale residuals over subjects within groups. These tests are closely…

基于风险函数的残差性质及其对模型诊断的含义AI 解读

Model diagnostic procedures in failure time models using hazard-based residuals rely on the assumption that the residual vector closely resembles a random sample from a unit exponential distribution when the model holds. This article formally investigates the validity of this critical assumption by deriving and examining the properties of parametrically, semiparametrically, and nonparametrically estimated residuals for complete and right-censored data. The joint distribution…

半参数回归泛函AI 解读

A regression method is developed for a general class of functionals. A semiparametric linear model is adopted, and the regression parameters are estimated by maximizing a profiled nonparametric or empirical likelihood based on a local estimate of the conditional distribution function. Simulated and real data examples are shown, including an application of quantile regression to censored survival data from a clinical trial for myeloma.

保存肿瘤标本取样方案的贝叶斯分析AI 解读

Intratumor DNA heterogeneity—as assessed by flow-cytometric cellular DNA analysis—is predictive of prognosis in many types of cancer. But some truly heterogeneous tumors apparently have a substantial chance of being misclassified as normal. One way to enhance the assay's sensitivity is to test multiple samples from each tumor specimen. This article describes an analysis of data from a study of endometrial cancer, with a view to establishing the number of samples needed to…

随机游走的若干方面及应用AI 解读

Introductory comments the ubiquitous characteristic function asymptotic properties and the diffusion limit lattice walks boundaries and constraints multistate random walks selected applications.

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摘要暂缺

This article extends Royall's (1992) results on optimal and robust sampling strategies to cluster sampling. It also gives the lower bound on the model-based variances of best linear unbiased predictors of finite population totals under certain classes of superpopulation models.

摘要暂缺

利用奥卡姆窗口进行图模型选择并处理模型不确定性AI 解读

We consider the problem of model selection and accounting for model uncertainty in high-dimensional contingency tables, motivated by expert system applications. The approach most used currently is a stepwise strategy guided by tests based on approximate asymptotic P values leading to the selection of a single model; inference is then conditional on the selected model. The sampling properties of such a strategy are complex, and the failure to take account of model uncertainty…

组序贯临床试验：贝叶斯决策论设计的经典统计评价AI 解读

Bayesian decision-theoretic designs for a clinical trial comparing two treatments for a disease with binary outcomes are developed and evaluated. The probability of successful outcome with treatment i is denoted by pi , i = 1, 2, and prior knowledge regarding each pi is assumed to follow a beta distribution. The pi are assumed to be independent. To facilitate comparison with frequentist clinical trial designs, we take a hypothesis-testing approach. The null hypothesis is δ <…

合并受控与非受控研究结果的随机效应元分析模型AI 解读

A random effects model is used to analyze meta-analyses containing both controlled and uncontrolled studies. A noniterative estimator of the treatment effect is derived using least squares, with the between-study variance substituted by an empirical Bayes estimator. The estimator is shown to be strongly consistent when the between-study variance is known, and the variance estimator is also shown to be strongly consistent. The estimator is shown to have desirable heuristic…

回归误差相关性的置换检验AI 解读

This article is about tests for serial, spatial, or other correlation in e, the error vector in the linear model Y = Xβ + e. The errors need not come from a particular parametric distribution such as the normal. P values are computed using permutations of the regression residuals. In the special cases that Y = e or X is a vector of Is, the tests are valid and consistent. In general, regression residuals are not exchangeable, so the tests are only approximate. It is shown,…

生存数据中的充分随访与异常值检验AI 解读

A situation in which a sample of failure times with many of the largest times censored may be taken as evidence of a proportion of “immune” or “cured” individuals, who are not subject to failure, in the population. A plot of the Kaplan-Meier empirical distribution function for such data will tend to level off near its right extreme, provided that follow-up of individuals has been continued for long enough. This article develops a diagnostic test for sufficient follow-up in…

单纯形上广义Liouville分布的依赖性质AI 解读

Compositional data arise naturally in several branches of science, including chemistry, geology, biology, medicine, ecology, and manufacturing design. Thus the correct statistical analysis of this type of data is of fundamental importance. Prior to the pioneering and extensive work of Aitchison, the Dirichlet distribution provided the parametric model of choice when analyzing such data. But Aitchison and others have since pointed out that the Dirichlet distribution is…

相干可靠性系统中的竞争风险：参数情形下的估计AI 解读

A coherent reliability system is a machine composed of a number of components that fails as soon as the set of failed components reaches certain fatal set-thresholds. On failure of the machine, an autopsy report reveals its time of failure and the set of failed components. I use incomplete data methods to obtain maximum likelihood estimates of parameters characterizing the lifetime distributions of the components, based on a sample of autopsy reports.

非线性时间序列的非参数模型辨识：投影方法AI 解读

We study the possibility of identifying general linear and nonlinear time series models using nonparametric methods. The kernel estimators of the conditional mean and variance are used as a basis, and the properties of these quantities as model indicators are briefly discussed. Some drawbacks are pointed out, and motivated by these we introduce projections as tools of identification. The projections are especially useful for additive modeling. Expressions for the asymptotic…

比例风险模型的分组持续时间分析：最小卡方估计与设定检验AI 解读

This article develops a semiparametric, minimum chi-squared estimation method of the proportional hazard model for the case when durations are grouped and covariates are categorical. The proposed estimator is easy to compute, yet asymptotically as efficient as the maximum likelihood estimator. This article also suggests simple specification tests for the proportional hazard model. If proportionality holds, then two sets of minimum chi-squared estimators, one from a further…

正态回归中的最优非负不变部分正交二次估计AI 解读

This article explores best estimation (in some sense) of the variance matrix V of the vector of disturbances in a normal linear regression model. More precisely, we consider the regression model y = Xβ + U, where U is distributed as N(0, V) and where the spectral form of V is V = Σn j1 λjRj. The R j are known and the λ j are the (possibly) distinct positive eigenvalues we wish to estimate. More generally, we wish to estimate a linear combination of the eigenvalues. This…

基于似然模型的半参数回归AI 解读

A weighted likelihood is used to estimate the parameters in a semiparametric model involving two covariates and allowing an association between the covariates. The development is for arbitrary but specified densities of the observations. The estimators are consistent and asymptotically normal. Hypothesis testing of the parametric component can be performed using a Wald test. Simulations and analysis of data with Bernoulli observations demonstrate the estimators' application.…

曲线估计的小波方法AI 解读

The theory of wavelets is a developing branch of mathematics with a wide range of potential applications. Compactly supported wavelets are particularly interesting because of their natural ability to represent data with intrinsically local properties. They are useful for the detection of edges and singularities in image and sound analysis and for data compression. But most of the wavelet-based procedures currently available do not explicitly account for the presence of noise…

快速稳健的多重异常值检测方法AI 解读

A few repeats of a simple forward search from a random starting point are shown to provide sufficiently robust parameter estimates to reveal masked multiple outliers. The stability of the patterns obtained is exhibited by the stalactite plot. The robust estimators used are least median of squares for regression and the minimum volume ellipsoid for multivariate outliers. The forward search also has potential as an algorithm for calculation of these parameter estimates. For…

Cox模型中若干Bootstrap置信区间的比较AI 解读

We study bootstrap confidence intervals for three types of parameters in Cox's proportional hazards model: the regression parameter, the survival function at fixed time points, and the median survival time at fixed values of a covariate. Several types of bootstrap confidence intervals are studied, and the type of interval is determined by two factors. One factor is the method of drawing the bootstrap sample. We consider three such methods: (1) ordinary resampling from the…