A two-parameter estimator in the negative binomial regression model

In this article, a two-parameter estimator is proposed to combat multicollinearity in the negative binomial regression model. The proposed two-parameter estimator is a general estimator which includes the maximum likelihood (ML) estimator, the ridge estimator (RE) and the Liu estimator as special cases. Some properties on the asymptotic mean-squared error (MSE) are derived and necessary and sufficient conditions for the superiority of the two-parameter estimator over the ML estimator and sufficient conditions for the superiority of the two-parameter estimator over the RE and the Liu estimator in the asymptotic mean-squared error (MSE) matrix sense are obtained. Furthermore, several methods and three rules for choosing appropriate shrinkage parameters are proposed. Finally, a Monte Carlo simulation study is given to illustrate some of the theoretical results.     

Kernel density estimation using weighted data ∗

In this paper we compare the kernel density estimators proposed by Bhattacharyya et al. (1988) and Jones (1991) for length biased data, showing the asymptotic normality of the estimators. A method to construct a new estimator is proposed. Moreover, we extend these results to weighted data and we study an estimator for the weight function.     

A comparative study of some bias correction techniques for kernel- based density estimators

Methods for obtaining kernel-based density estimators with lower bias and mean integrated squared error than an estimator based on a standard Normal kernel function are described and discussed. Three main approaches are considered which are: firstly by using 'optimal' polynomial kernels as described, for example, by Gasser er a1 (1985); secondly by employing generalised jackknifing as proposed by Jones nd Foster (1993) and thirdly by subtracting an estimator of the principal asymptotic bias term from the original estimator. The emphasis in this initial discussion is on their asymptotic properties. The finite sample performance of those that have the best asymptotic properties are compared with two adaptive estimators, as well as the fixed Normal kernel estimator, in a simulation study.     

Generalized kernel regression estimator for dependent size-biased data

This paper considers nonparametric regression estimation in the context of dependent biased nonnegative data using a generalized asymmetric kernel. It may be applied to a wider variety of practical situations, such as the length and size biased data. We derive theoretical results using a deep asymptotic analysis of the behavior of the estimator that provides consistency and asymptotic normality in addition to the evaluation of the asymptotic bias term. The asymptotic mean squared error is also derived in order to obtain the optimal value of smoothing parameters required in the proposed estimator. The results are stated under a stationary ergodic assumption, without assuming any traditional mixing conditions. A simulation study is carried out to compare the proposed estimator with the local linear regression estimate.     

Asymptotic distribution of regression correlation coefficient for Poisson regression model

This study treats an asymptotic distribution for measures of predictive power for generalized linear models (GLMs). We focus on the regression correlation coefficient (RCC) that is one of the measures of predictive power. The RCC, proposed by Zheng and Agresti is a population value and a generalization of the population value for the coefficient of determination. Therefore, the RCC is easy to interpret and familiar. Recently, Takahashi and Kurosawa provided an explicit form of the RCC and proposed a new RCC estimator for a Poisson regression model. They also showed the validity of the new estimator compared with other estimators. This study discusses the new statistical properties of the RCC for the Poisson regression model. Furthermore, we show an asymptotic normality of the RCC estimator.     

A family of estimators of population variance in two-occasion rotation patterns

Abstract

In this article, we have considered the problem of estimation of population variance on current (second) occasion in two occasion successive (rotation) sampling. A class of estimators of population variance has been proposed and its asymptotic properties have been discussed. The proposed class of estimators is compared with the sample variance estimator when there is no matching from the previous occasion and the Singh et al. (2013) estimator. Optimum replacement policy is discussed. It has been shown that the suggested estimator is more efficient than the Singh et al. (2013) estimator and a usual unbiased estimator when there is no matching. An empirical study is carried out in support of the present study.     

Goodness-of-fit test under length-biased sampling

In this article, we study a goodness-of-fit (GOF) test in the presence of length-biased sampling. For this purpose, we introduce a smoothed estimator of distribution function (d.f.) and we investigate its asymptotic behaviors, such as uniform consistency and asymptotic normality. Based on this estimator, we define a one-sample Kolmogorov type of GOF test for length-biased data. We conduct Monte Carlo simulations to evaluate the performance of the proposed test statistic and compare it with the one-sample Kolmogorov type of GOF test obtained by the non smoothed estimator of d.f.     

First hitting probabilities for semi-Markov chains and estimation

We first consider a stochastic system described by an absorbing semi-Markov chain (SMC) with finite state space, and we introduce the absorption probability to a class of recurrent states. Afterwards, we study the first hitting probability to a subset of states for an irreducible SMC. In the latter case, a non-parametric estimator for the first hitting probability is proposed and the asymptotic properties of strong consistency and asymptotic normality are proven. Finally, a numerical application on a five-state system is presented to illustrate the performance of this estimator.     

Ordinary and weighted least-squares estimators

We propose a method of estimating the asymptotic relative efficiency (ARE) of the weighted least-squares estimator (WLSE) with respect to the ordinary least-squares estimator (OLSE) in a heteroscedastic linear regression model with a large number of observations but a small number of replicates at each value of the regressors. The weights used in the WLSE are the reciprocals of the (within-group) average of squared residuals. It is shown that the OLSE is more efficient than the WLSE if the maximum number of replicates is not larger than two. The proposed estimator of the ARE is consistent as the number of observations tends to infinity. Finite-sample performance of this estimator is examined in a simulation study. An adaptive estimator, which is asymptotically more efficient than the OLSE and the WLSE, is proposed.     

Wavelet estimation of density for censored data with censoring indicator missing at random

In this paper, we define the nonlinear wavelet estimator of density for the right censoring model with the censoring indicator missing at random (MAR), and develop its asymptotic expression for mean integrated squared error (MISE). Unlike for kernel estimator, the MISE expression of the estimator is not affected by the presence of discontinuities in the curve. Meanwhile, asymptotic normality of the estimator is established. The proposed estimator can reduce to the estimator defined by Li [Non-linear wavelet-based density estimators under random censorship. J Statist Plann Inference. 2003;117(1):35–58] when the censoring indicator MAR does not occur and a bandwidth in non-parametric estimation is close to zero. Also, we define another two nonlinear wavelet estimators of the density. A simulation is done to show the performance of the three proposed estimators.     

Practical considerations of the jackknife estimator of variance for generalized estimating equations

Lipsitz, Dear and Zhao (1994) proposed a “one-step” Jackknife estimator of the variance based on Wu's (1986) jackknife and showed its asymptotic equivalence to the robust variance estimator of White (1982) and Liang and Zeger (1986). In this paper an asymptotically equivalent estimator is proposed which avoids the Newton-Raphson or Fisher scoring step of the estimator proposed by Lipsitz, Dear and Zhao. Hence, summation in univariate models can be avoided.     

Combining poisson means

The problem of estimating the Poisson mean is considered based on the two samples in the presence of uncertain prior information (not in the form of distribution) that two independent random samples taken from two possibly identical Poisson populations. The parameter of interest is λ₁ from population I. Three estimators, i.e. the unrestricted estimator, restricted estimator and preliminary test estimator are proposed. Their asymptotic mean squared errors are derived and compared; parameter regions have been found for which restricted and preliminary test estimators are always asymptotically more efficient than the classical estimator. The relative dominance picture of the estimators is presented. Maximum and minimum asymptotic efficiencies of the estimators relative to the classical estimator are tabulated. A max-min rule for the size of the preliminary test is also discussed. A Monte Carlo study is presented to compare the performance of the estimator with that of Kale and Bancroft (1967).     

Data sharpening on unknown manifold

This article is concerned with data sharpening (DS) technique in nonparametric regression under the setting where the multivariate predictor is embedded in an unknown low-dimensional manifold. Theoretical asymptotic bias is derived, which reveals that the proposed DS estimator has a reduced bias compared to the usual local linear estimator. The asymptotic normality of the DS estimator is also developed. It can be confirmed from simulation and applications to real data that the bias reduction for the DS estimator supported on unknown manifold is evident.     

A local linear estimation of conditional hazard function in censored data

A local linear estimator of the conditional hazard function in censored data is proposed. The estimator suggested in this paper is motivated by the ideas of Fan, Yao, and Tong (1996) and Kim, Bae, Choi, and Park (2005). The asymptotic distribution of the proposed estimator is derived, and some numerical results are also provided.     

ROBUST ESTIMATION FOR A SIMPLE EXPONENTIAL MODEL1

A Hodges-Lehmann type estimator (Hodges and Lehmann, 1963) is proposed for the parameter p in the simple exponential model (1) y=1-exp.(-ρx)+ε Some exact and asymptotic properties of the proposed estimator are also given.     

Self-weighted quasi-maximum exponential likelihood estimator for ARFIMA-GARCH models

In this paper, a local self-weighted quasi-maximum exponential likelihood estimator for ARFIMA-GARCH models is proposed, asymptotic normality of this estimator is derived under the existence of second moment including stationary and non-stationary cases. A simulation study is given to evaluate the performance of the proposed self-weighted QMELE under the stationary case.     

Adjusting regression attenuation in the Cox proportional hazards model

In the measurement error Cox proportional hazards model, the naive maximum partial likelihood estimator (MPLE) is asymptotically biased. In this paper, we give the formula of the asymptotic bias for the additive measurement error Cox model. By adjusting for this error, we derive an adjusted MPLE that is less biased. The bias can be further reduced by adjusting for the estimator second and even third time. This estimator has the advantage of being easy to apply. The performance of the proposed estimator is evaluated through a simulation study.     

A note on calibration weightings for stratified double sampling with equal probability

This study proposes a more efficient calibration estimator for estimating population mean in stratified double sampling using new calibration weights. The variance of the proposed calibration estimator has been derived under large sample approximation. Calibration asymptotic optimum estimator and its approximate variance estimator are derived for the proposed calibration estimator and existing calibration estimators in stratified double sampling. Analytical results showed that the proposed calibration estimator is more efficient than existing members of its class in stratified double sampling. Analysis and evaluation are presented.     

Pooling means under uncertain prior information with application to discrete distributions

The problem of pooling means is considered based on two samples in presence of the uncertain prior information that these samples are taken from possibly identical populations. Two discrete models, Poisson and binomial are considered in particular. Three estimators, i.e. the unrestricted estimator, shrinkage restricted estimator and estimators based on preliminary test are proposed. Their asymptotic mean squared errors are derived and compared. It is demonstrated via asymptotic results that the range of the parameter space in which shrinkage preliminary test estimator dominates the unrestricted estimator is wider than that of the usual preliminary test estimator. A Monte Carlo study for Poisson model is presented to compare the performance of the estimators for small samples.     

Estimating the survival function based on the semi-Markov model for dependent censoring

In this paper, we study a nonparametric maximum likelihood estimator (NPMLE) of the survival function based on a semi-Markov model under dependent censoring. We show that the NPMLE is asymptotically normal and achieves asymptotic nonparametric efficiency. We also provide a uniformly consistent estimator of the corresponding asymptotic covariance function based on an information operator. The finite-sample performance of the proposed NPMLE is examined with simulation studies, which show that the NPMLE has smaller mean squared error than the existing estimators and its corresponding pointwise confidence intervals have reasonable coverages. A real example is also presented.