Some properties of the length of the shortest half

This paper discusses some properties of the length of the shortest half proposed by Rousseeuw and Leroy (1988) as a robust scale estimator.     

Testing equality of variances in the analysis of repeated measurements

The problem of comparing the precisions of two instruments using repeated measurements can be cast as an extension of the Pitman-Morgan problem of testing equality of variances of a bivariate normal distribution. Hawkins (1981) decomposes the hypothesis of equal variances in this model into two subhypotheses for which simple tests exist. For the overall hypothesis he proposes to combine the tests of the subhypotheses using Fisher's method and empirically compares the component tests and their combination with the likelihood ratio test. In this paper an attempt is made to resolve some discrepancies and puzzling conclusions in Hawkins's study and to propose simple modifications.
The new tests are compared to the tests discussed by Hawkins and to each other both in terms of the finite sample power (estimated by Monte Carlo simulation) and theoretically in terms of asymptotic relative efficiencies.     

MSE-improvement of the least squares estimator by dropping variables

It is well known that dropping variables in regression analysis decreases the variance of the least squares (LS) estimator of the remaining parameters. However, after elimination estimates of these parameters are biased, if the full model is correct. In his recent paper, Boscher (1991) showed that the LS-estimator in the special case of a mean shift model (cf. Cook and Weisberg, 1982) which assumes no “outliers” can be considered in the framework of a linear regression model where some variables are deleted. He derived conditions under which this estimator outperforms the LS-estimator of the full model in terms of the mean squared error (MSE)-matrix criterion. We demonstrate that this approach can be extended to the general set-up of dropping variables. Necessary and sufficient conditions for the MSE-matrix superiority of the LS-estimator in the reduced model over that in the full model are derived. We also provide a uniformly most powerful F-statistic for testing the MSE-improvement.     

On the human aspects in structural modeling

This article deals with two facets of structural modeling often ignored: a) the several human roles that effective participative modeling must encompass, and b) the group procedures developed to assist modelers in defining the elements of the system to be modeled. The roles are 1) the method technician, 2) the facilitator, and 3) the participant. Their recognition on the part of the technology assessment leader is vital to the successful conduct of participative modeling. The element-generating group procedures surveyed here are organized into two categories: those which emphasize an atmosphere for free-wheeling thinking, and those which emphasize structured guidance (either through use of words or geometric and analytic techniques).     

On the theory of macroeconomic quasi-equilibria

Conclusion It has been shown that for the Classical System a quasi-equilibrium cannot exist, unless we make the ad hoc assumption of inflexible nominal wages⁸. The equilibrium in the classical regime corresponds to the general competitive equilibrium, and of course the validity of Walras' Law cannot be questioned. At the same time, however, it has been shown that to extend these conclusions to the Keynesian system as well is not justified. The Keynesian system has, in general, a quasi-equilibrium. The model constructed in this paper and the resulting conclusions are significant because the model: (a) Incorporates the Keynesian notion of effective demand, which includes the demand for capital goods (investment) as being performed by a group of people distinct from the consumers (and so, answering Negishi's point, there is a prince in Hamlet!), (b) Unlike other models (like the recent paper by Glustoff), it does not rely on nominal wage rigidity to explain unemployment, but instead, again answering Negishi's remark, it explains rather than postulates why real wages do not adjust in the presence of unemployment so as to eliminate it. (c) It verifies the validity of Clower's proposition that in the Keynesian System Walras' Law holds only in equilibrium. (d) It reconsiles Bent Hansen's original quasi-equilibrium model with the Keynesian proposition of an unemployment equilibrium, against the apparent view of Hansen that to do that would require the assumption of a Phillips curve, a view also shared by Arrow and Hahn, and many others.An earlier version of this paper was presented in the December 1974 meeting of the Econometric Society in San Francisco. The author wishes to thank Prof. R. Clower, Prof. B. Hansen, Prof. S. Black, and Dr. G. Winckler for their valuable comments, but he obviously claims any errors for himself.     

Putting supplies at the bedside via the Friesen concept

Hospitals designed using the concepts of architect Gordon Friesen are especially conducive to reengineering for patient-focused care. The Nurserver, a closet-like space outside each patient's room, makes it very easy for hospitals to redesign their methods for delivering supplies so that caregivers seldom have to go more than a few feet to get what they need. In this article, staff of Monongalia General Hospital in Morgantown, West Virginia, describe how they have used the Friesen design to modify supply distribution processes.     

Measuring the savings from managed care: experience at Citibank

In a leap of faith, Citibank in 1989 designed a point-of-service plan aimed at containing health care costs in the long term without sacrificing quality of care. In 1994 a study was undertaken to empirically evaluate whether these goals had been achieved. The study supported Citibank's overall managed care strategy, providing objective, quantifiable data that can lead to greater efficiencies.     

Making competition in health care work

Health care reform in the United States is on a collision course with economic reality. Most proposals focus on measures that will produce one-time cost savings by eliminating waste and inefficiency. But the right question to ask is how to achieve dramatic and sustained cost reductions over time. What will it take to foster entirely new approaches to disease prevention and treatment, whole new ways to deliver services, and more cost-effective facilities? The answer lies in the powerful lessons business has learned over the past two decades about the imperatives of competition. In industry after industry, the underlying dynamic is the same: competition compels companies to deliver constantly increasing value to customers. The fundamental driver of this continuous quality improvement and cost reduction is innovation. Without incentives to sustain innovation in health care, short-term cost savings will soon be overwhelmed by the desire to widen access, the growing health needs of an aging population, and the unwillingness of Americans to settle for anything less than the best treatments available. The misguided assumption underlying much of the debate about health care is that technology is the enemy. By assuming that technology drives up costs, reformers neglect the central importance of innovation or, worse yet, attempt to slow its pace. In fact, innovation, driven by rigorous competition, is the key to successful reform.