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Multiple change‐point detection for regression curves 回归曲线的多变化点检测
Pub Date : 2024-07-25 DOI: 10.1002/cjs.11816
Yunlong Wang
Nonparametric estimation of a regression curve becomes crucial when the underlying dependence structure between covariates and responses is not explicit. While existing literature has addressed single change‐point estimation for regression curves, the problem of multiple change points remains unresolved. In an effort to bridge this gap, this article introduces a nonparametric estimator for multiple change points by minimizing a penalized weighted sum of squared residuals, presenting consistent results under mild conditions. Additionally, we propose a cross‐validation‐based procedure that possesses the advantage of being tuning‐free. Our simulation results showcase the competitive performance of these new procedures when compared with state‐of‐the‐art methods. As an illustration of their utility, we apply these procedures to a real dataset.
当协变量和响应之间的基本依赖结构不明确时,回归曲线的非参数估计就变得至关重要。现有文献已经解决了回归曲线的单变化点估计问题,但多变化点问题仍未解决。为了缩小这一差距,本文通过最小化受惩罚的加权残差平方和,介绍了一种多变化点的非参数估计方法,并在温和条件下给出了一致的结果。此外,我们还提出了一种基于交叉验证的程序,该程序具有无需调整的优点。我们的模拟结果表明,与最先进的方法相比,这些新程序的性能极具竞争力。为了说明这些程序的实用性,我们将其应用于一个真实的数据集。
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引用次数: 0
An SIR‐based Bayesian framework for COVID‐19 infection estimation 基于 SIR 的 COVID-19 感染估计贝叶斯框架
Pub Date : 2024-07-13 DOI: 10.1002/cjs.11817
Haoyu Wu, David A. Stephens, Erica E. M. Moodie
Estimating the COVID‐19 infection fatality rate, inferring the latent incidence and predicting the future epidemic evolution are critical to public health surveillance, but often challenging due to limited data availability or quality. Recently, a Bayesian framework combining time series deconvolution of deaths with a parametric Susceptible–Infectious–Recovered (SIR) model was proposed by Irons and Raftery, 2021. We assess the parameter identifiability of the model using the profile likelihood approach and simulations, when only the time series of deaths and seroprevalence survey data are available. The robustness of the model to the more complex but also more realistic Susceptible–Exposed–Infectious–Recovered (SEIR)‐based epidemics is evaluated through simulations; the influence of potential biases in the serosurveys on the inference is also investigated. We use a stationary first‐order autoregressive prior to account for the variability of transmission rate over time. The results suggest that the model is relatively robust to SEIR‐based epidemics, especially when the reproductive number is low, given sufficient information from serosurveys or priors. However, the lack of parameter identifiability under limited data availability cannot be neglected. We apply the model to infer the COVID‐19 infections in Ontario and Quebec, Canada during the Omicron era.
估算 COVID-19 感染致死率、推断潜伏发病率和预测未来疫情演变对公共卫生监测至关重要,但由于数据可用性或质量有限,这往往具有挑战性。最近,Irons 和 Raftery 于 2021 年提出了一个贝叶斯框架,该框架将死亡时间序列解卷积与参数化的易感-感染-恢复(SIR)模型相结合。在只有死亡时间序列和血清流行率调查数据的情况下,我们使用轮廓似然法和模拟来评估模型的参数可识别性。通过模拟,我们评估了该模型对更复杂但也更现实的基于易感-暴露-感染-康复(SEIR)的流行病的稳健性;我们还研究了血清调查中的潜在偏差对推断的影响。我们使用静态一阶自回归先验来考虑传播率随时间的变化。结果表明,在血清调查或先验信息充足的情况下,该模型对基于 SEIR 的流行病相对稳健,尤其是当繁殖数量较低时。然而,在数据有限的情况下,缺乏参数可识别性的问题不容忽视。我们应用该模型推断了 Omicron 时代加拿大安大略省和魁北克省的 COVID-19 感染情况。
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引用次数: 0
Robust estimation of loss‐based measures of model performance under covariate shift 基于损失的模型性能测量方法在协变量偏移情况下的稳健估算
Pub Date : 2024-07-12 DOI: 10.1002/cjs.11815
Samantha Morrison, Constantine Gatsonis, Issa J. Dahabreh, Bing Li, Jon A. Steingrimsson
We present methods for estimating loss‐based measures of the performance of a prediction model in a target population that differs from the source population in which the model was developed, in settings where outcome and covariate data are available from the source population but only covariate data are available on a simple random sample from the target population. Prior work adjusting for differences between the two populations has used various weighting estimators with inverse odds or density ratio weights. Here, we develop more robust estimators for the target population risk (expected loss) that can be used with data‐adaptive (e.g., machine learning‐based) estimation of nuisance parameters. We examine the large‐sample properties of the estimators and evaluate finite‐sample performance in simulations. Last, we apply the methods to data from lung cancer screening using nationally representative data from the National Health and Nutrition Examination Survey (NHANES) and extend our methods to account for the complex survey design of the NHANES.
我们提出了一些方法,用于估算基于损失的预测模型在目标人群中的性能测量值,目标人群不同于开发模型的源人群,在这种情况下,源人群的结果和协变量数据可用,而目标人群的简单随机样本只有协变量数据可用。之前针对两个人群之间的差异进行调整的工作使用了各种加权估计器,包括反向几率加权或密度比加权。在此,我们为目标人群风险(预期损失)开发了更稳健的估计器,可用于数据自适应(如基于机器学习)的滋扰参数估计。我们检查了估计器的大样本特性,并通过模拟评估了有限样本性能。最后,我们将这些方法应用于肺癌筛查数据,使用的是美国国家健康与营养调查(NHANES)中具有全国代表性的数据,并对我们的方法进行了扩展,以考虑到 NHANES 复杂的调查设计。
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引用次数: 0
Estimating the mean squared prediction error of the observed best predictor associated with small area counts: A computationally oriented approach 估算与小面积计数相关的观测最佳预测因子的均方预测误差:面向计算的方法
Pub Date : 2024-07-06 DOI: 10.1002/cjs.11810
Thuan Nguyen, Jiming Jiang
We consider estimation of the mean squared prediction error (MSPE) for observed best prediction (OBP) in small area estimation with count data. The OBP method has been previously developed in this context by Chen et al. (Journal of Survey Statistics and Methodology, 3, 136–161, 2015). However, estimation of the MSPE remains a challenging problem due to potential model misspecification that is considered in this setting. The latter authors proposed a bootstrap method for estimating the MSPE, whose theoretical justification is not clear. We propose to use a Prasad–Rao‐type linearization method to estimate the MSPE. Unlike the traditional linearization approaches, our method is computationally oriented and easier to implement in the same regard. Theoretical properties and empirical performance of the proposed method are studied. A real‐data application is considered.
我们考虑在使用计数数据进行小面积估算时,对观测最佳预测(OBP)的均方预测误差(MSPE)进行估算。此前,Chen 等人已在此背景下开发了 OBP 方法(《调查统计与方法学期刊》,3,136-161,2015 年)。然而,由于在这种情况下要考虑潜在的模型错误规范,MSPE 的估计仍然是一个具有挑战性的问题。后一位作者提出了一种估计 MSPE 的 bootstrap 方法,但其理论依据并不明确。我们建议使用 Prasad-Rao 型线性化方法来估计 MSPE。与传统的线性化方法不同,我们的方法以计算为导向,更易于实现。我们研究了所提方法的理论特性和经验性能。还考虑了实际数据应用。
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引用次数: 0
Estimation in a general mixture of Markov jump processes 马尔可夫跳跃过程的一般混合物的估计
Pub Date : 2024-06-30 DOI: 10.1002/cjs.11814
Halina Frydman, Budhi Arta Surya
We propose a general mixture of Markov jump processes. The key novel feature of the proposed mixture is that the generator matrices of the Markov processes comprising the mixture are entirely unconstrained. The Markov processes are mixed with distributions that depend on the initial state of the mixture process. The maximum likelihood (ML) estimates of the mixture's parameters are obtained from continuous realizations of the mixture process and their standard errors from an explicit form of the observed Fisher information matrix, which simplifies the Louis (Journal of the Royal Statistical Society Series B, 44:226–233, 1982) general formula for the same matrix. The asymptotic properties of the ML estimators are also derived. A simulation study verifies the estimates' accuracy. The proposed mixture provides an exploratory tool for identifying the homogeneous subpopulations in a heterogeneous population. This is illustrated with an application to a medical dataset.
我们提出了马尔可夫跳跃过程的一般混合物。所提混合物的关键新特征是,构成混合物的马尔可夫过程的生成矩阵完全不受制约。马尔可夫过程的混合分布取决于混合过程的初始状态。混合物参数的最大似然法(ML)估计是从混合物过程的连续实化中获得的,其标准误差是从观察到的费雪信息矩阵的明确形式中获得的,这简化了路易斯(《皇家统计学会杂志》B 辑,44:226-233, 1982 年)关于同一矩阵的一般公式。此外,还得出了 ML 估计数的渐近特性。模拟研究验证了估计的准确性。所提出的混合物为识别异质人群中的同质子群提供了一种探索性工具。我们将通过对一个医疗数据集的应用来说明这一点。
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引用次数: 0
Order‐restricted hypothesis tests for nonlinear mixed‐effects models with measurement errors in covariates 具有协变量测量误差的非线性混合效应模型的限阶假设检验
Pub Date : 2024-06-29 DOI: 10.1002/cjs.11812
Yixin Zhang, Wei Liu, Lang Wu
Order‐restricted hypothesis testing problems frequently arise in practice, including studies involving regression models for longitudinal data. These tests are known to be more powerful than tests that ignore such restrictions. In this article, we consider order‐restricted tests for nonlinear mixed‐effects models with measurement errors in time‐dependent covariates. We propose to use a multiple imputation method to address measurement errors, since this approach allows us to use existing complete‐data methods for order‐restricted tests. Some theoretical results are presented. We evaluate our proposed methods via simulation studies that demonstrate they are more powerful than either a competing naive method or a two‐step approach to testing hypotheses. We illustrate the use of our proposed approach by analyzing data from an HIV/AIDS study.
在实践中,包括涉及纵向数据回归模型的研究中,经常会出现有序限制的假设检验问题。众所周知,这些检验比忽略此类限制的检验更有效。在本文中,我们将考虑对具有时间协变量测量误差的非线性混合效应模型进行阶次限制检验。我们建议使用多重估算方法来解决测量误差问题,因为这种方法允许我们使用现有的完整数据方法进行阶次限制检验。我们提出了一些理论结果。我们通过模拟研究对我们提出的方法进行了评估,结果表明,这些方法比与之竞争的天真方法或两步假设检验方法更强大。我们通过分析一项艾滋病毒/艾滋病研究的数据来说明我们提出的方法的用途。
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引用次数: 0
Tests for the first‐order stochastic dominance 一阶随机优势检验
Pub Date : 2024-06-23 DOI: 10.1002/cjs.11811
Weiwei Zhuang, Peiming Wang, Jiahua Chen
We study the first‐order stochastic dominance (SD) test in the context of two independent random samples. We introduce several test statistics that effectively capture violations of the dominance relationship, particularly in the tail regions. Additionally, we develop a resampling procedure to compute the ‐values or critical values for these tests. The proposed tests have asymptotic type I error rates for frontal configurations equal to the nominal level . Furthermore, their powers approach 1 for any fixed alternatives. Through simulation experiments, we demonstrate that our SD tests outperform the recentring test proposed by Donald and Hsu (2016) as well as the integral‐type test presented by Linton et al. (2010) in various scenarios discussed in existing literature. We also employ the proposed tests to analyze changes in the distribution of household income in the United Kingdom over time. The proposed tests offer some insights into potential dominance relationships within this context.
我们在两个独立随机样本的背景下研究了一阶随机支配(SD)检验。我们引入了几种检验统计量,它们能有效捕捉违反支配关系的情况,尤其是在尾部区域。此外,我们还开发了一种重采样程序,用于计算这些检验的-值或临界值。所提出的检验对于正面配置的渐近 I 型错误率等于标称水平。此外,对于任何固定的替代方案,它们的幂都接近 1。通过模拟实验,我们证明在现有文献讨论的各种情况下,我们的 SD 检验优于 Donald 和 Hsu(2016 年)提出的重整检验以及 Linton 等人(2010 年)提出的积分型检验。我们还利用提出的检验分析了英国家庭收入分布随时间的变化。在此背景下,所提出的检验为潜在的支配关系提供了一些见解。
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引用次数: 0
Tolerance bands for exponential family functional data 指数族函数数据的容差带
Pub Date : 2024-06-23 DOI: 10.1002/cjs.11808
Galappaththige S. R. de Silva, Pankaj K. Choudhary
A tolerance band for a functional response provides a region that is expected to contain a given fraction of observations from the sampled population at each point in the domain. This band is a functional analogue of the tolerance interval for a univariate response. Although the problem of constructing functional tolerance bands has been considered for a Gaussian response, it has not been investigated for non‐Gaussian responses, which are common in biomedical applications. We describe a methodology for constructing tolerance bands for two non‐Gaussian members of the exponential family: binomial and Poisson. The approach is to first model the data using the framework of generalized functional principal components analysis. Then, a parameter is identified in which the marginal distribution of the response is stochastically monotone. We show that the tolerance limits can be readily obtained from confidence limits for this parameter, which in turn can be computed using large‐sample theory and bootstrapping. Our proposed methodology works for both dense and sparse functional data. We report the results of simulation studies designed to evaluate its performance and get recommendations for practical applications. We illustrate our proposed method using two actual biomedical studies, and also provide computer source code that implements our method.
函数式响应的容差带提供了一个区域,该区域预计会包含域中每个点上来自采样人群的特定部分的观测值。该容限带与单变量响应的容限区间类似。虽然构建功能容差带的问题已针对高斯响应进行过考虑,但对于生物医学应用中常见的非高斯响应,还没有进行过研究。我们介绍了一种为指数家族中的两个非高斯成员(二项式和泊松)构建容差带的方法。该方法首先使用广义函数主成分分析框架建立数据模型。然后,确定响应边际分布随机单调的参数。我们的研究表明,从该参数的置信区间可以很容易地得到容差极限,而置信区间又可以通过大样本理论和引导法来计算。我们提出的方法既适用于密集函数数据,也适用于稀疏函数数据。我们报告了旨在评估其性能的模拟研究结果,并为实际应用提出了建议。我们使用两个实际的生物医学研究来说明我们提出的方法,并提供了实现我们方法的计算机源代码。
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引用次数: 0
Regression trees for interval‐censored failure time data based on censoring unbiased transformations and pseudo‐observations 基于普查无偏变换和伪观测的间隔删失故障时间数据回归树
Pub Date : 2024-06-21 DOI: 10.1002/cjs.11807
Ce Yang, Xianwei Li, Liqun Diao, Richard J. Cook
Interval‐censored data arise when a failure process is under intermittent observation and failure status is only known at assessment times. We consider the development of predictive algorithms when training samples involve interval censoring. Using censoring unbiased transformations and pseudo‐observations, we define observed data loss functions, which are unbiased estimates of the corresponding complete data loss functions. We show that regression trees based on these loss functions can recover the tree structure and yield good predictive accuracy. An application is given to a study involving individuals with psoriatic arthritis where the aim is to identify genetic markers useful for the prediction of axial disease within 10 years of a baseline assessment.
当故障过程受到间歇性观测,且故障状态仅在评估时间已知时,就会出现区间剔除数据。我们考虑了在训练样本涉及区间删失的情况下开发预测算法的问题。通过使用无偏剔除变换和伪观测,我们定义了观测数据损失函数,这些函数是对相应完整数据损失函数的无偏估计。我们证明,基于这些损失函数的回归树可以恢复树结构,并产生良好的预测精度。我们将其应用到一项涉及银屑病关节炎患者的研究中,该研究的目的是找出有助于预测基线评估后 10 年内轴向疾病的遗传标记。
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引用次数: 0
Constrained Bayes in multiplicative area‐level models under the precautionary loss function 预防性损失函数下乘法区域级模型中的受限贝叶斯
Pub Date : 2024-06-20 DOI: 10.1002/cjs.11809
Elaheh Torkashvand, Mohammad Jafari Jozani
Consider the problem of benchmarking small‐area estimates under multiplicative models with positive parameters. The goal is to propose a loss function that guarantees positive constrained estimates of small‐area parameters in this situation. The weighted precautionary loss function is introduced to solve the problem. Compared with the weighted Kullback–Leibler (KL) loss function, our proposed loss function penalizes underestimation of the small‐area parameters of interest more for small values of parameters. This property is appealing when we estimate disease rates. It tends to give larger estimates of small‐area parameters compared with those obtained under the KL loss function. The hierarchical empirical Bayes and constrained hierarchical empirical Bayes estimates of small‐area parameters and their corresponding risk functions under the new proposed loss function are obtained. The performance of the proposed methods is investigated using simulation studies and a real dataset.
考虑在参数为正的乘法模型下对小面积估计值进行基准测试的问题。我们的目标是提出一种损失函数,以保证在这种情况下小面积参数的正约束估计值。为了解决这个问题,引入了加权预防损失函数。与加权库尔巴克-莱伯勒(KL)损失函数相比,我们提出的损失函数对小参数值的小面积参数低估的惩罚更大。当我们估算疾病发病率时,这一特性很有吸引力。与 KL 损失函数相比,它倾向于给出更大的小区域参数估计值。在新提出的损失函数下,得到了小区域参数的分层经验贝叶斯估计值和受约束分层经验贝叶斯估计值及其相应的风险函数。利用模拟研究和真实数据集对所提方法的性能进行了研究。
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引用次数: 0
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The Canadian Journal of Statistics
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