论文检索

拟合混合效应Logistic模型时混合分布误设的影响AI 解读

Mixed-effects logistic models are often used to analyze binary response data which have been gathered in clusters, or groups. Responses are assumed to follow a logistic model with in clusters, with an intercept which varies across clusters according to a specified probability distribution G. In this paper we examine the performance of mixed-effects logistic regression analysis when a main component of the model, the mixture distribution, is misspecified. We show that, when…

生存与计划处死实验中约束极大似然估计的显式解AI 解读

Regulatory agencies routinely base conclusions regarding carcinogenicity of compounds tested in long-term animal studies on tests which are known to be biased under conditions of treatment lethality and tumour lethality. The recognition of these biases has led to a variety of proposed approaches which rely on survival and sacrifice data. Williams & Portier (1992) derived analytic expressions for maximum likelihood estimators of the tumour incidence rate and discrete death…

线性模型中的 Jackknife 方差估计量AI 解读

An alternative to the weighted jackknife variance estimator of Wu (1986) is introduced. Motivated by the comments of Efron (1986), Ghosh (1986) and Tibshirani (1986), the performance of Wu's estimator is compared with the proposed estimator in terms of the average loss in some linear models. Some asymptotic properties of the proposed estimator are discussed.

由渐近展开启发的插值规则AI 解读

We suggest a simple interpolation rule, based on Edgeworth and Cornish-Fisher expansions, which permits highly accurate numerical approximation in problems involving calculation of distributions or quantiles without requiring explicit calculation of terms in the expansions.

多元家庭数据的主成分分析AI 解读

The use of a principal component analysis is considered for multivariate data on families with different numbers of siblings. The coefficients in principal components are given as the eigenvectors of the weighted sums of squares and products matrix from the sibling data. Asymptotic distributions of the eigenvalues and eigenvectors of the estimated covariance matrix are obtained for an elliptical population. Asymptotic distributions of statistics associated with reduction of…

线性模型中不等式约束与单侧假设的稳健检验AI 解读

For the linear regression model with independent and identically distributed errors, robust tests of various hypotheses on the regression parameter are developed; by ‘robust’, we mean robustness of size and power against long-tailed error distributions which may not be symmetric. The proposed test statistic, denoted by FM, resembles the usual F-statistic. The two main results are (i) under the null hypothesis, the asymptotic distribution of FM and that of the least squares…

极小极大最优设计构造的统一方法AI 解读

We present a unified approach for constructing large-sample optimal designs when the optimality criterion is of the minimax type. The assumed model is a general linear regression model with a known efficiency function defined on a closed and bounded space. An equivalence theorem is formulated and computer algorithms for generating minimax optimal designs are proposed. It is shown that this methodology is simple and rather general. It can be used to construct, for example,…

区组设计中双处理与单处理的比较AI 解读

Experiments having two treatment factors and one blocking factor are considered in which a particular combination of treatment factor levels must be excluded. The motivation for the work is a medical trial of two drugs in which a double placebo cannot be administered on ethical grounds. The contrasts of interest compare the effects of having both treatment factors at nonzero labelled levels with the effects of having only one treatment factor at a nonzero labelled level. A…

利用频数数据和单次捕获样本进行捕获—再捕获估计AI 解读

One way in which a capture-recapture experiment can be designed is to count each capture occasion as a separate sample, and tally the number of individuals caught once, twice, and so on. This paper discusses the estimators currently used for this type of experiment, and suggests some new ones. Each of the estimators is categorized by its derivation. Following this, their properties are discussed, particularly their bias and variance, with the aim of choosing one or two of…

结合逻辑回归与比例风险回归的混合模型AI 解读

A model is proposed for the analysis of censored data which combines a logistic formulation for the probability of occurrence of an event with a proportional hazards specification for the time of occurrence of the event. The proposed model is a semiparametric generalization of a parametric model due to Farewell (1982). Estimates of the regression parameters are obtained by maximizing a Monte Carlo approximation of a marginal likelihood and the EM algorithm is used to…

生存数据马尔可夫模型的非参数检验AI 解读

Jones & Crowley (1989) introduced a general class of nonparametric statistics for right-censored survival data that includes many of the existing procedures involving a single covariate. This paper considers this class in the framework of a Markov model and suggests some tests especially appropriate for the Markov setting. Application to left-truncated and right-censored data is also given. Small sample properties and asymptotic relative efficiencies for several statistics…

删失多元失效时间数据的协方差与生存函数估计AI 解读

The covariance between counting process martingales is used to characterize the dependence between two failure time variates. A representation of the bivariate survivor function is obtained in terms of the marginal survivor functions and this covariance function. A closely related representation expresses the bivariate survivor function in terms of marginal survivor functions and a conditional covariance function, leading to a new nonparametric survivor function estimator.…

配对数据中的处理效应异质性AI 解读

Data from matched pairs are often analysed under the assumption that treatment effects are homogeneous. We develop tests of this assumption, with Poisson and binomial examples. Mixture models for inference when overdispersion is present are investigated, with stress on matched pairs of counts.

二元响应筛查的稳健设计AI 解读

Optimal screening procedures are derived using Bayesian decision theory. A simple heuristic solution is determined using an asymptotic posterior distribution for the parameters in a linear probit model. The solution is shown to be optimal within a class of possible procedures and robust to departures from model assumptions.

合并规则不确定时整合不同实验结果的贝叶斯方法AI 解读

Given data from several experiments or observational studies initially believed to be similar, it is desired to estimate the means corresponding to one or more experiments of particular interest. To illustrate the proposed methodology we consider a simple specification where there are no covariates. A class of prior distributions for the set, μ = (μ1,…, μL), of experiment means is specified to reflect the beliefs that (a) there are subsets of μ such that the μ1's within each…

有限总体分布函数估计量的性质AI 解读

Two leading estimators of the finite population distribution function are studied. Their large-sample mean squared errors are compared, under a given model. Neither estimator is universally better; circumstances are identified where the model-based estimator would do poorly, despite employing the correct model.

再捕获模型中的捕获同质性检验AI 解读

This paper presents a new method of testing capture homogeneity in recapture experiments where there is time homogeneity. The basic set of statistics used is a lower triangular matrix whose (i, k)th element is the proportion of those animals caught on the next (i + 1)st occasion who have been caught k times until now. Both theoretical and simulation evidence is presented that the new procedure is superior to methods previously suggested.

利用加速寿命模型调整协变量的序贯对数秩检验AI 解读

This paper presents a simple sequential method for comparing two treatments in randomized clinical trials which allows for the adjustment of other covariates with the accelerated life model. The new procedure is the same as the ordinary sequential log rank test except that the test statistic is calculated on an ‘adjusted’ time scale. This covariate adjustment can lead to more efficient designs of group sequential trials especially when the effects of covariates being…

Siegel 复合周期性检验统计量的渐近分位点AI 解读

Fisher's test for a periodicity at a single Fourier frequency is often inadequate in practice where it is necessary to test for compound periodicities, i.e. spectral lines at several frequencies. Siegel (1980) derived a test statistic for compound periodicity and provided percentage points for m not exceeding 50, where N = 2m + 1 is the length of the time series. Here the distribution of the test statistic is rewritten to enable computation of exact percentage points for m…

多组临床试验中针对有序备择的非参数序贯检验AI 解读

In a multiple-armed clinical trial where one agent is administered at several dose levels or where each treatment regimen is formed by adding more agents to the preceding combination, it is desirable to use test statistics that are sensitive to alternatives of stochastically ordered distributions. Liu et al (1992) recently developed a class of such test statistics by taking linear combinations of the familiar two-sample weighted log rank statistics. In the present paper, we…

剖面似然与修正剖面似然差异札记AI 解读

The difference between profile likelihood and modified profile likelihood depends primarily on the expected value of a certain third order derivative of the log likelihood. It is shown that in exponential family problems this derivative vanishes if the parameter of interest is a mean parameter but in general not when it is a canonical parameter. As examples some matched pair problems for exponential family models are considered.

不完整数据下泊松对数线性模型的观测信息矩阵AI 解读

We consider inferences about Poisson log linear models for which only certain disjoint sums of the data are observable. We derive an explicit formula for the observed information matrix associated with the log linear parameters that is intuitively appealing and simple to evaluate.

基于累积卡方统计量最大分量的多重比较程序AI 解读

Multiple comparison procedures based on the maximal component of the cumulative chi-squared statistic are discussed. The Markov properties for the successive components of the cumulative chi-squared statistic are proved and applied for obtaining the p- value of the maximal component in each of the one-way and the two-way analysis of variance models and the two-way contingency table. The power of the multiple comparison procedure is compared with those for some well-known…

实验设计稳健性的新视角AI 解读

A common practical experimental philosophy when the underlying response model is unknown is initially to consider a first order model. A total robustness approach requires that the experimenter account for model underspecification due to possible curvature or interactions. It is reasonable that the experimental design possess protection against the selection of an oversimplified model. However, detection of possible underspecification is also important. This paper introduces…