Estimable functions in the nonlinear model

When the method of least squares is used to estimate the parameters in a general model and the generated system of normal equations is linearly dependent, the estimate of the vector of parameters which satisfies the criterion is not unique. However, there exist certain functions of the estimated vector of parameters which are invariant to the least squares solution obtained from the normal equations. We define those invariant functions to be estimable, and present a technique to determine the functions of the parameters which are estimable for the general model. The method results in solving either a linear first order partial differential equation or a system of linear first order partial differential equations corresponding, respectively, to a single or multiple dependency between columns of the Jacobian matrix of the mean of the model. The usual results concerning estimability for linear models are a special case of the general results developed.     

Defending the city

Abstract

In ‘Defending the City’ George Pattison seeks to defend the modern city against the charge — made, for example, by Graham Ward — that it is a merely secular phenomenon. Instead, he argues that, in its essence, it is multi‐dimensional and pluralistic, representing a range of diverse possibilities, creative as well as destructive. Also, the modern city is shown to anticipate the essential features of the postmodern city. The argument is illustrated by references to Pugin's critique of architectural eclecticism, to Dostoevsky's invocation of the fantastical reality of St. Petersburg, to Kierkegaard and to Murnau's film Sunrise. It is claimed that the best Christian response to the city is to defend, not to subvert, its pluralism.     

On Necessary and Sufficient Conditions for Ordinary Least Squares Estimators to Be Best Linear Unbiased Estimators

Two often-quoted necessary and sufficient conditions for ordinary least squares estimators to be best linear unbiased estimators are described. Another necessary and sufficient condition is described, providing an additional tool for checking to see whether the covariance matrix of a given linear model is such that the ordinary least squares estimator is also the best linear unbiased estimator. The new condition is used to show that one of the two published conditions is only a sufficient condition.     

Computational and statistical efficiency of semiparametric gls estimators

In this note, we report a dramatic improvement in the computational efficiency of semiparametric generalized least squares(SGLS) estimation. Computation of SGLS estimates no longer presents serious problems with data sets of moderate size. We also correct a numerical error in the standard errors of the SGLS estimates reported in our recent paper in this journal (Horowitz and Neumann, 1987). The corrected standard errors of SGLS are comparable to those we reported for quantile estimates.     

A Comparison of Ethical Practices of Russian and American Managers

This study examines perception of various business practices of Russian and American managers. Using data collected from 136 Russian managers and 252 American managers we found that cross-national differences account for many differences between perceptions of business practices. Implications for managerial practice are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Estimation of Location Parameters Under Nonnormal Errors and Quadratic Loss

Assuming a statistical model in which the joint distribution of the unobservable errors is drawn from independent univariate Student t's that are identically and symmetrically distributed, the sampling performance of traditional robust estimators and a family of Stein-like estimators are compared and evaluated. These results suggest that under thick-tailed distributions, the relative sampling performances and risk characteristics for a range of nonconventional Stein estimators remains approximately the same as in the case of their normal counterparts. The empirical risk implications of misspecifying the error distribution are investigated.     

Building capacity for urban management in Ghana: some critical considerations

Severe capacity gaps continue to constrain effective urban management in Ghana, despite numerous donor-supported training programmes. This paper examines the nature of these capacity gaps and analyses specifically the factors contributing to the low attraction and retention of local government staff: politicisation of the bureaucracy, excessive use of external experts, excessive state intervention in skill development and low remuneration of local government staff. Against this background, the paper reviews critically a recent capacity building initiative: the establishment of the (new) Institute of Local Government Studies in Accra. Suggestions to improve capacity building for urban management in Ghana are offered. These include the need to prepare a coherent strategy to guide and co-ordinate stakeholder inputs in capacity building; to place training in the context of institutional development; and encourage the development and use of local expertise in donor assisted projects; and, promote merit-based remuneration of local government staff.