Medical students' and tutors' experiences of directed and self-directed learning programs in evidence-based medicine: a qualitative evaluation accompanying a randomized controlled trial

This qualitative study aims to interpret the results of a randomized controlled trial comparing two educational programs (directed learning and self-directed learning) in evidence-based medicine (EBM) for medical students at the University of Oslo from 2002 to 2003. There is currently very little comparative educational research in this field. In the trial, no statistically significant differences between the study groups were shown for any outcomes considered (EBM knowledge, skills, and attitudes). Further analysis suggests that main reason for the negative trial results was that the majority of students learned equally effectively, whichever program they received, although implementation of the educational programs was not complete because of varying attendance. This study illustrates a stepwise evaluation model that might be useful in evaluating other socially complex interventions.     

A neoclassical Kaldor model of real wage declines

A model linking macroeconomic equilibrium and income distribution in balanced growth equilibria is developed as a variant to the Kaldor model of factor shares. It departs from the original Kaldor model in assuming equal saving rates and a neoclassical production function. Macroeconomic equilibrium (national savings equal to investment) combines with competitive microeconomic behavior to determine the real wage and real interest rate. An increase in the ratio of national debt to labor reduces the real wage, explaining recent declines.     

On value-judgements and ethics in health technology assessment

The widespread application of technology in health care has imposed a broad range of challenges. The field of health technology assessment (HTA) is developed in order to face some of these challenges. However, this strategy has not been as successful as one could hope. One of the reasons for this is that social and ethical considerations have not been integrated in the HTA process. Nowadays however, such considerations have been included in many HTAs. Still, the conclusions and recommendations of the HTAs are not followed. The reason for this may be that the methods for integrating ethics for HTA are not sufficiently developed, or that they are not adequate. This article presents a supplementary approach to the ethical inquiry in HTA. It is argued that a value analysis is crucial in order to address the ethical issues of health care technology in a fruitful way and to make viable decisions about such technology.

On Loss Distributions from Installment-Repaid Loans

The banks have been accumulating huge data bases for many years and are increasingly turning to statistics to provide insight into customer behaviour, among other things. Credit risk is an important issue and certain stochastic models have been developed in recent years to describe and predict loan default. Two of the major models currently used in the industry are considered here, and various ways of extending their application to the case where a loan is repaid in installments are explored. The aspect of interest is the probability distribution of the total loss due to repayment default at some time. Thus, the loss distribution is determined by the distribution of times to default, here regarded as a discrete-time survival distribution. In particular, the probabilities of large losses are to be assessed for insurance purposes.     

Conflicting strategic objectives in hospital design

This paper presents a multigoal linear programming model designed to analyse the impact of different strategic objectives in the planning of hospitals. The paper argues that it is necessary to adopt an overall point-of-view in planning; that it is necessary to consider the interactions between the hospital, other social and health institutions and the community at large in order to attain an efficient plan. A simplified cost-benefit analysis is suggested, and it is demonstrated that the opportunity costs of lost working days may be more important than both capital and operating costs from a social point of view.     

Optimal Ordering Policies for Stochastic Inventory Problems with Observed Information Delays

Information delays exist in an inventory system when it takes time to collect, process, validate, and transmit inventory/demand data. A general framework is developed in this paper to describe information flows in an inventory system with information delays. We characterize the sufficient statistics for making optimal decisions. When the ordering cost is linear, the optimality of a state‐dependent base‐stock policy is established even when information flows are allowed to cross over time. Additional insights into the problem are obtained via a comparison between our models and the models with stochastic order lead times. We also show that inventory can substitute for information and vice versa.     

On sequentially rejective subset selection procedures

A technique for selection procedures, called sequential rejection, is investigated. It is shown that this technique is posssible to apply to certain selection goals of the "all or nothing" type, i.e. "selecting a subset containing all good populations" or "selecting a subset containing no bad population". The analogy with existing sequential techniques in the general theory of simultaneous statistical inference is pointed out.     

Some further aspects of the löwner-ordering antitonicity of the moore-penrose inverse

A survey is given of known proofs of the antitonicity of the inverse matrix function for positive definite matrices w.r.t. the Lowner partial ordering, and of the corresponding result for the Moore-Penrose inverse of nonnegative definite matrices [the theorem of Milliken and Akdeniz (1977)]. A short new proof of the latter result is obtained by employing an extremal representation of a nonnegative definite quadratic form. Another proof of this result involving Schur complements is also given, and is seen to be extendable to the case of symmetric (not necessarily nonnegative definite) matrices. A geometrical interpretation of Milliken and Akdeniz's theorem is presented. As an application, the relationship between the concepts of greater (maximum) concentration and smaller (minimum) dispersion is considered for a pair (class) of vector-valued statistics with possibly degenerate distributions.     

Iterative bias reduction: a comparative study

Multivariate nonparametric smoothers, such as kernel based smoothers and thin plate splines smoothers, are adversely impacted by the sparseness of data in high dimension, also known as the curse of dimensionality. Adaptive smoothers, that can exploit the underlying smoothness of the regression function, may partially mitigate this effect. This paper presents a comparative simulation study of a novel adaptive smoother (IBR) with competing multivariate smoothers available as package or function within the R language and environment for statistical computing. Comparison between the methods are made on simulated datasets of moderate size, from 50 to 200 observations, with two, five or 10 potential explanatory variables, and on a real dataset. The results show that the good asymptotic properties of IBR are complemented by a very good behavior on moderate sized datasets, results which are similar to those obtained with Duchon low rank splines.