共查询到12条相似文献,搜索用时 6 毫秒
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We propose a class of multidimensional Item Response Theory models for polytomously-scored items with ordinal response categories. This class extends an existing class of multidimensional models for dichotomously-scored items in which the latent abilities are represented by a random vector assumed to have a discrete distribution, with support points corresponding to different latent classes in the population. In the proposed approach, we allow for different parameterizations for the conditional distribution of the response variables given the latent traits, which depend on the type of link function and the constraints imposed on the item parameters. Moreover, we suggest a strategy for model selection that is based on a series of steps consisting of selecting specific features, such as the dimension of the model (number of latent traits), the number of latent classes, and the specific parameterization. In order to illustrate the proposed approach, we analyze a dataset from a study on anxiety and depression on a sample of oncological patients. 相似文献
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Qie Li 《统计学通讯:理论与方法》2013,42(23):5071-5090
We propose a Bayesian hierarchical model for multiple comparisons in mixed models where the repeated measures on subjects are described with the subject random effects. The model facilitates inferences in parameterizing the successive differences of the population means, and for them, we choose independent prior distributions that are mixtures of a normal distribution and a discrete distribution with its entire mass at zero. For the other parameters, we choose conjugate or vague priors. The performance of the proposed hierarchical model is investigated in the simulated and two real data sets, and the results illustrate that the proposed hierarchical model can effectively conduct a global test and pairwise comparisons using the posterior probability that any two means are equal. A simulation study is performed to analyze the type I error rate, the familywise error rate, and the test power. The Gibbs sampler procedure is used to estimate the parameters and to calculate the posterior probabilities. 相似文献
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在今天越来越激烈的市场竞争之中,越来越多的公司已经从产品驱动的市场竞争策略转向客户驱动的市场竞争策略。并且随着计算机技术及数据挖掘方法的飞速发展,直接市场营销越来越受到重视。如何选择目标客户邮寄货单的问题也就越来越引起市场直销者的兴趣。计分模型及增益表选择方法和单群预测及选择方法是目前普遍采用的两种客户选择方法。在平稳市场的假设下,客户的购买模式服从著名的重复购买理论。基于这个理论,本文提出了一种新的客户选择方法,即两群预测及选择方法。应用实际的客户数据比较这三种不同的方法,结果表明新方法表现最好。 相似文献
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Walter W. Hauck 《The American statistician》2013,67(2):158-160
A problem in logit analysis is the interval estimation of the logistic response curve. Scheffé's method is used to obtain confidence bands for the logistic response function for any number of explanatory variables. This method is computationally easier and more general than a previously reported method. 相似文献
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Junfeng Shang 《统计学通讯:理论与方法》2013,42(6):1095-1109
Repeated measurements are collected in a variety of situations and are generally characterized by a mixed model where the correlation within the subject is specified by the random effects. In such a mixed model, we propose a multiple comparison procedure based on a variant of the Schwarz information criterion (SIC; Schwarz, 1978). The derivation of SIC indicates that SIC serves as an asymptotic approximation to a transformation of the Bayesian posterior probability of a candidate model. Therefore, an approximated posterior probability for a candidate model can be calculated based upon SIC. We suggest a variant of SIC which includes the terms which are asymptotically negligible in the derivation of SIC. The variant improves upon the performance of SIC in small and moderate sample-size applications. Based upon the proposed variant, the corresponding posterior probability can be calculated for each candidate model. A hypothesis testing for multiple comparisons involves one or more models in the candidate class, the posterior probability of the hypothesis testing is therefore evaluated as the sum of the posterior probabilities for the models associated with the testing. The approximated posterior probability based on the variant accommodates the effect of the prior on each model in the candidate class, and therefore is more effectively approximated than that based on SIC for conducting multiple comparisons. We derive the computational formula of the approximated posterior probability based on the variant in the mixed model. The applications in two real data sets demonstrate that the proposed procedure based on the SIC variant can perform effectively in multiple comparisons. 相似文献
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In Bayesian Inference it is often desirable to have a posterior density reflecting mainly the information from sample data. To achieve this purpose it is important to employ prior densities which add little information to the sample. We have in the literature many such prior densities, for example, Jeffreys (1967), Lindley (1956); (1961), Hartigan (1964), Bernardo (1979), Zellner (1984), Tibshirani (1989), etc. In the present article, we compare the posterior densities of the reliability function by using Jeffreys, the maximal data information (Zellner, 1984), Tibshirani's, and reference priors for the reliability function R(t) in a Weibull distribution. 相似文献
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《统计学通讯:理论与方法》2013,42(10):2409-2422
Abstract A simple method based on sliced inverse regression (SIR) is proposed to explore an effective dimension reduction (EDR) vector for the single index model. We avoid the principle component analysis step of the original SIR by using two sample mean vectors in two slices of the response variable and their difference vector. The theories become simpler, the method is equivalent to the multiple linear regression with dichotomized response, and the estimator can be expressed by a closed form, although the objective function might be an unknown nonlinear. It can be applied for the case when the number of covariates is large, and it requires no matrix operation or iterative calculation. 相似文献
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多元极值的参数建模方法及其金融应用:最新进展述评 总被引:1,自引:0,他引:1
由于现实中的极值事件往往倾向于同时或相继发生,因此多元极值研究正成为极值统计学的理论前沿和研究热点。本文对该领域中参数建模方法的最新进展做了系统性述评,包括经典多元极值理论、Ledford-Tawn-Ramos方法和Heffernan和Tawn条件法等,并指出了这些建模方法的优缺点以及未来可能的理论突破点。本文还全面分析了近年来多元极值分析方法在金融领域的国内外应用现状,并探讨其未来的应用前景,可能是在金融传染、组合问题和系统性风险管理等方面。 相似文献
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Nicole H. Augustin Stefan Lang Monica Musio Klaus von Wilpert 《Journal of the Royal Statistical Society. Series C, Applied statistics》2007,56(1):29-50
Summary. The data that are analysed are from a monitoring survey which was carried out in 1994 in the forests of Baden-Württemberg, a federal state in the south-western region of Germany. The survey is part of a large monitoring scheme that has been carried out since the 1980s at different spatial and temporal resolutions to observe the increase in forest damage. One indicator for tree vitality is tree defoliation, which is mainly caused by intrinsic factors, age and stand conditions, but also by biotic (e.g. insects) and abiotic stresses (e.g. industrial emissions). In the survey, needle loss of pine-trees and many potential covariates are recorded at about 580 grid points of a 4 km × 4 km grid. The aim is to identify a set of predictors for needle loss and to investigate the relationships between the needle loss and the predictors. The response variable needle loss is recorded as a percentage in 5% steps estimated by eye using binoculars and categorized into healthy trees (10% or less), intermediate trees (10–25%) and damaged trees (25% or more). We use a Bayesian cumulative threshold model with non-linear functions of continuous variables and a random effect for spatial heterogeneity. For both the non-linear functions and the spatial random effect we use Bayesian versions of P -splines as priors. Our method is novel in that it deals with several non-standard data requirements: the ordinal response variable (the categorized version of needle loss), non-linear effects of covariates, spatial heterogeneity and prediction with missing covariates. The model is a special case of models with a geoadditive or more generally structured additive predictor. Inference can be based on Markov chain Monte Carlo techniques or mixed model technology. 相似文献
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This article suggests an efficient method of estimating a rare sensitive attribute which is assumed following Poisson distribution by using three-stage unrelated randomized response model instead of the Land et al. model (2011) when the population consists of some different sized clusters and clusters selected by probability proportional to size(:pps) sampling. A rare sensitive parameter is estimated by using pps sampling and equal probability two-stage sampling when the parameter of a rare unrelated attribute is assumed to be known and unknown.We extend this method to the case of stratified population by applying stratified pps sampling and stratified equal probability two-stage sampling. An empirical study is carried out to show the efficiency of the two proposed methods when the parameter of a rare unrelated attribute is assumed to be known and unknown. 相似文献