FITTING SPATIAL CORRELATION MODELS: APPROXIMATING A LIKELIHOOD APPROXIMATION

The paper considers a class of spatial correlation models (stationary Gaussian processes) which includes (spatial) conditional autoregressive, simultaneous autoregressive, moving average and direct covariance models. Given observations on a finite rectangular lattice, a likelihood approximation for estimating the parameters in the spectral density of the model is discussed. The approximation consists of applying the trapezoidal rule, with a her grid of frequencies than the usual Fourier frequencies, to compute the integral in an appraximation due to Whittle (1954) and later modified by Guyon (1984). With this approximation, a Fisher scoring type algorithm has a simple form and in some casea reduces to iteratively reweighted least squares. Methods for computing the unbiased two-dimensional periodogram required by the method are presented and the accuracy of the approximation is discussed. The asymptotic distribution of the parameter estimates computed from the likelihood approximation is also given.     

Testing for linearity in simple regression models

In this paper a new test is introduced which checks the linearity assumption in bivariate regression models. It is based on the idea that the slope through the data points (x_i,y_i) and (x_j,y_j) should be approximately equal to the slope through the data points (x_j,y_j) and (x_k,y_k) for x_i<x_j<x_k under the assumption that the random variable Y is a linear function of the independent variable x. This idea is formalized in a U-statistic on which the test for linearity is based. The test performs well for the considered case of power transformations, which is of high practical relevance.     

吉林省林业产业结构灰色动态关联分析

该文运用灰色关联度模型理论，计算了1997--2006年吉林省林业产业结构的灰色关联度，并在此基础上，对吉林省林业产业结构灰色动态关联关系进行了全面分析，提出了吉林省林业产业结构调整的对策和建议。     

A weighted spatial median for clustered data

A weighted spatial median is proposed for the multivariate one-sample location problem with clustered data. Its limiting distribution is derived under mild conditions (no moment assumptions) and it is shown to be multivariate normal. Asymptotic as well as finite sample efficiencies and breakdown properties are considered, and the theoretical results are supplied with illustrative examples. It turns out that there is a potential for meaningful gains in estimation efficiency: the weighted spatial median has superior efficiency to the unweighted spatial median particularly when the cluster sizes are widely disparate and in the presence of strong intracluster correlation. The unweighted spatial median for clustered data was considered earlier by Nevalainen et al. (Can J Statist, in press, 2007). The proposed weighted estimators provide companion estimates to the weighted affine invariant sign test proposed recently by Larocque et al. (Biometrika, in press, 2007). An affine equivariant weighted spatial median is discussed in parallel.     

HFC－134a水平管内对流换热实验研究

本文对ＨＦＣ－１３４ａ水平管内单相对流换热进行了实验研究．用实验所获数据与常用换热关系式进行了比较，计算结果表明Ｐｅｔｕｋｈｏｖ和Ｔａｋａｍａｔｓｕ关系式与实验数据吻合较好．本文最后用实验数据拟合出一个ＨＦＣ－１３４ａ管内单相对流换热关系式，在给定的范围内，其算术平均误差为０．１６４％．绝对平均误差为４．９６８％．     

教育程度与工资收入相关性的中外比较

本文从中外比较的角度对教育程度与工资收入之间的相关关系进行了实证分析 ,初步论证了教育程度是影响个人工资收入的重要因素 ,并得出若干结论。同时本文也对我国现行工资制度、用人制度的改革提出了若干建议     

General class of estimators in multi-character surveys

In this paper, a general class of estimators for the estimation of a finite population total in multi-character surveys is proposed. It is shown that the estimators proposed by Arnab (2002), Amahiaet al. (1989) and Bansal and Singh (1985) are the special cases of the proposed class of estimators. The proposed class of estimators is always more efficient than the estimator proposed by Rao (1966).     

Genetic correlation of wing polymorphism between females and males in the oriental chinch bug,Cavelerius saccharivorus Okajima (Heteroptera: Lygaeidae)

Summary Genetic correlations of the wing form and the relative wing length between females and males were estimated in the oriental chinch bug,Cavelerius saccharivorus, by calculating the correlation between the sexes of the proportion macropterous or the mean relative wing length in full-sib families obtained from different wing forms of parents emerged in a high density population. There was a significantly positive genetic correlation between the sexes in both the proportion macropterous and the mean relative wing length. However, the appearance rate of macropters tended to be much lower in males than in females under the rearing conditions which promote the appearance of macropters. This was evident especially in the offspring of brachypterous parents. These indicated that inC. saccharivorus the wing polymorphism of males is not a simple result of the genetic correlation of wing morphology between the two sexes. It was considered that both of the female and male fitness advantages to wing reduction, as well as the genetic correlation between the sexes, would influence the evolution of wing polymorphism in this species.     

Mathematical Modeling of Reproductive and Developmental Toxic Effects for Quantitative Risk Assessment

A new mathematical dose-response model for reproductive and developmental risk assessment is proposed. The model includes the possibility of an exposure threshold as well as a litter-size effect. Correlation of responses of offspring from the same litter is taken into account through the use of the beta-binomial distribution. Confidence limits for low-dose extrapolation are based on the asymptotic distribution of the likelihood ratio. An empirical comparison of the proposed procedure to that of Rai and Van Ryzin demonstrates the improvement that can be achieved with the new procedure.     

IS THE ASSUMPTION OF UNIFORM INTRA-CLASS CORRELATION EVER NEEDED?

When modelling a finite population it is sometimes assumed that the residuals from the regression model expectations are distributed with a uniform non-zero intra-class correlation. It is shown that if a certain vector is spanned by the columns of the design matrix (in the homoskedastic case this vector corresponds to the inclusion of a constant term) then such a model is underidentified and the assumption of a known non-zero correlation has almost no impact on the results of the regression analysis. When this vector is not spanned by the columns of the design matrix, a simpler alternative model can usually be fitted equally well to observations from any single population. The only exception occurs when the the intra-class correlation required is negative in sign.