Small area estimation for spatially correlated populations - a comparison of direct and indirect model-based methods

Linear mixed models underpin many small area estimation (SAE) methods. In this paper we investigate SAE based on linear models with spatially correlated small area effects where the neighbourhood structure is described by a contiguity matrix. Such models allow efficient use of spatial auxiliary information in SAE. In particular, we use simulation studies to compare the performances of model-based direct estimation (MBDE) and empirical best linear unbiased prediction (EBLUP) under such models. These simulations are based on theoretically generated populations as well as data obtained from two real populations (the ISTAT farm structure survey in Tuscany and the US Environmental Monitoring and Assessment Program survey). Our empirical results show only marginal gains when spatial dependence between areas is incorporated into the SAE model

The BLUE in continuous-time regression models with correlated errors

In this paper, the problem of best linear unbiased estimation is investigated for continuous-time regression models. We prove several general statements concerning the explicit form of the best linear unbiased estimator (BLUE), in particular when the error process is a smooth process with one or several derivatives of the response process available for construction of the estimators. We derive the explicit form of the BLUE for many specific models including the cases of continuous autoregressive errors of order two and integrated error processes (such as integrated Brownian motion). The results are illustrated on many examples

"On Measuring Uncertainty of Small Area Estimators with Higher Order Accuracy"

The empirical best linear unbiased predictor (EBLUP) or the empirical Bayes estimator (EB) in the linear mixed model is recognized useful for the small area estimation, because it can increase the estimation precision by using the information from the related areas. Two of the measures of uncertainty of EBLUP is the estimation of the mean squared error (MSE) and the confidence interval, which have been studied under the second-order accuracy in the literature. This paper provides the general analytical results for these two measures in the unified framework, namely, we derive the conditions on the general consistent estimators of the variance components to satisfy the third-order accuracy in the MSE estimation and the confidence interval in the general linear mixed normal models. Those conditions are shown to be satisfied by not only the maximum likelihood (ML) and restricted maximum likelihood (REML), but also the other estimators including the Prasad-Rao and Fay-Herriot estimators in specific models.

"Theory of Linear Mixed Models and its Applications to Small Area Estimation"(in Japanese)

Linear mixed models (LMM) and the best linear unbiased predictor (BLUP) have received considerable attention in recent years from both theoretical and practical aspects. This article reviews the theory of LMM and illustrates how useful LMM and BLUP are through an example of the small area estimation. Linear mixed models for analyzing longitudinal data are also explained and an application to the posted land price data is given.

"A Review of Linear Mixed Models and Small Area Estimation"

The linear mixed models (LMM) and the empirical best linear unbiased predictor (EBLUP) induced from LMM have been well studied and extensively used for a long time in many applications. Of these, EBLUP in small area estimation has been recognized as a useful tool in various practical statistics. In this paper, we give a review on LMM and EBLUP from a aspect of small area estimation. Especially, we explain why EBLUP is likely to be reliable. The reason is that EBLUP possesses the shrinkage function and the pooling effects as desirable properties, which arise from the setup of random effects and common paramers in LMM. Such important properties of EBLUP are clarified as well as some recent results of the mean squared error estimation, the confidence interval and the variable selection procedures are summarized.

Outliers and influence under arbitrary variance

Using a geometric approach to best linear unbiased estimation in the general linear model, the additional sum of squares principle, used to generate decompositions, can be generalized allowing for an efficient treatment of augmented linear models. The notion of the admissibility of a new variable is useful in augmenting models. Best linear unbiased estimation and tests of hypotheses can be performed through transformations and reparametrizations of the general linear model. The theory of outliers and influential observations can be generalized so as to be applicable for the general univariate linear model, where three types of outlier and influence may be distinguished. The adjusted models, adjusted parameter estimates, and test statistics corresponding to each type of outlier are obtained, and data adjustments can be effected. Relationships to missing data problems are exhibited. A unified approach to outliers in the general linear model is developed. The concept of recursive residuals admits generalization. The typification of outliers and influential observations in the general linear model can be extended to normal multivariate models. When the outliers in a multivariate regression model follow a nested pattern, maximum likelihood estimation of the parameters in the model adjusted for the different types of outlier can be performed in closed form, and the corresponding likelihood ratio test statistic is obtained in closed form. For an arbitrary outlier pattern, and for the problem of outliers in the generalized multivariate regression model, three versions of the EM-algorithm corresponding to three types of outlier are used to obtain maximum likelihood estimates iteratively. A fundamental principle is the comparison of observations with a choice of distribution appropriate to the presumed type of outlier present. Applications are not necessarily restricted to multivariate normality

A study of estimators in linear models

This thesis is a study of Estimators, particularly in Linear Models. The newest technology of Bootstrap Methodology is employed in the estimation procedure. We present a survey of the Bootstrap Methodology in the beginning and move on to some serious problems in Linear Model estimation procedure. We have worked out the conditions under which the estimators of nonstandard linear models will be best linear unbiased estimators. Furthermore, we have shown that the estimators of other linear models bear a linear relationship with least squares estimators. Finally, we have worked out the finite sample properties of two-stage least-squares using the Bootstrap Methodology