Relative efficiencies of some simple Bayes estimators of coefficients in dynamic models — I

In this paper we consider some approximations to Bayes estimators of coefficients in simple autoregressive models and give an example of a Monte Carlo experiment where these approximate Bayes estimators yield a substantial improvement over the usual sampling theory or quasi-Bayesian estimators. The practical situation is represented by the case where the coefficient vector is known to lie in or on a hypersphere of radius r with center at 0. We show that arbitrariness in the choice of the value of r is often not catastrophic if r is sufficiently large, but finite.     

Regional variations in entrepreneurial cognitions: Start-up intentions of university students in Spain

Empirical research has recently paid considerable attention to the role of environmental factors in explaining regional variations in entrepreneurial activity. However, cognitive models have not usually included these factors in their analyses. Therefore, the main objective of this study is to identify some of the environmental cognitive elements that may explain regional differences in start-up intentions. Thus, an entrepreneurial intention model is developed, theoretically based on the planned behaviour approach, institutional economic theory and social capital theory. The empirical analysis is carried out using structural equation techniques over a sample of 549 final year university students from two Spanish regions (Catalonia and Andalusia). Results confirm that valuation of entrepreneurship in each region helps explain regional differences in entrepreneurial intentions. As expected, social valuation of the entrepreneur was higher in the more developed region (Catalonia), positively affecting perceived subjective norms and behavioural control. In Andalusia, the influence of perceived valuation of the entrepreneur in the closer environment was more important, affecting attitude towards the behaviour and subjective norms. These results explain some of the differences in the pool of potential entrepreneurs in each region. They also justify the need by public-policy decision-makers to promote more positive entrepreneurial values in relatively backward regions.     

A metafrontier directional distance function approach to assessing eco-efficiency

This paper uses directional distance functions to extend the non-parametric metafrontier approach to efficiency measurement proposed by O’Donnell et al. (Empir Econ 34:231–255, 2008) to the assessment of technological differences in eco-efficiency between groups of producers. Furthermore, eco-efficiency is assessed at the level of specific environmental pressure management. This methodology is applied to a sample of Spanish olive producers that belong to both traditional mountain and traditional plain growing systems. We find great potential for both olive growing systems to reduce environmental pressures. In terms of pressures on natural resources, the most eco-efficient technology is the traditional plain system, while the traditional mountain system is the most eco-efficient when considering pressures on biodiversity. These results might help policymakers design strategies to improve the performance of olive growing and meet the demands of society regarding the economic and ecological functions of this farming activity.     

BP: developing excellence in the global enterprise

World-class supply management organizations like Honda of America, John Deere, Chrysler, Hewlett Packard, and Motorola all understand the power of continuous improvement in the supply base. The best supplier management and development programs help suppliers--on a long-term basis--develop their own strength and expertise in suggestion systems, new product development, and high quality production results.     

Age-test Markov chains for drug testing and detection

Random urinalysis strategies stratified by time since the last test are characterized with a set of Markov chain models. The probability of a person being tested depends on the amount of time since the person's last test. The Nuclear Regulatory Commission (NRC) has proposed a two strata drug testing strategy based on time since last test. The proposal included a high testing rate for people not yet tested in a given time period and a low testing rate for people testing negative in a given time period. Southern California Edison has implemented a variation of the NRC proposal. These strategies can be modeled within a Markov chain framework. Time to detection is calculated as a function of testing probabilities and drug usage levels. Drug user gaming strategies are discussed with illustrations. These models are implemented as part of a U.S. Navy drug policy analysis system.     

Off-site materiel management

Supplies for a chronic dialysis unit are critical to operations. Planning, training, and computer-assisted database management allow for successful management of supply purchasing, inventory control, receiving, and record-keeping by a technician without any prior materiel management experience.     

Compound gamma bivariate distributions

Summary Bivariate distributions, which may be of special relevance to the lifetimes of two components of a system, are derived using the following approach. As the two components are part of one system and therefore exposed to similar conditions of service, there will be similarity between their lifetimes that is not shared by components belonging to different systems. The lifetime distribution for a given system is assumed to be Gamma in form (this includes the exponential as a special case; extension to the Stacey distribution, which includes the Weibull distribution, is straightforward). The scale parameter of this distribution is itself a random variable, with a Gamma distribution. We thus obtain what might be termed a compound Gamma-Gamma bivariate distribution. The cumulative distribution function of this may be expressed in terms of one of the double hypergeometric functions of Appell.Generalised hypergeometric functions play an important part in this paper, and one of Saran's triple hypergeometric functions is obtained when generalising the above model to permit the scale parameters of the distributions for the two components to be correlated, rather than identical.Work started while the author was with the Transport Studies Group, University College London.     

A methodology for the assessment of ridesharing program benefits and impacts

Due to the increased cost and decreased availability of energy, many cities are developing experimental ridesharing programs. The evaluation of such public transportation programs often involves some form of benefit/cost analysis. In this paper we review a methodology proposed by Wagner for calculating ridesharing program benefits. We propose a modification for calculating vehicle-miles reduction and suggest a survey instrument for collecting the appropriate data. In addition, we present a surrogate measure which is simpler to compute and allows sensitivity analysis for incorporating certain intangible factors. Data from a survey conducted in the Greater Cincinnati area is used to illustrate the calculations. The results can be useful in evaluating other ridesharing programs.     

Measuring cost savings in the operating room: a matter of FOCUS (follow-through, obsolescence, control, utilization, standardization)

In summary, changes came slowly at first in the OR. The biggest inventory reduction came about a year after the effort had begun. It would seem that tackling obsolescence, standardizing products, etc. would give an initial "big chunk" savings, with small amounts coming later as inventories are lowered. What we expected did not occur, due to the inherent nature of practices and what was customarily being used. For example, previously, some equipment purchases were paid for by purchasing product, which resulted in long-term commitments and high supply costs. The OR at times seemed more like a process of managing change, not just supplies. FOCUS is a daily process. How many times can you afford to overlook this process? How often are the mistakes of the past repeated? In review, we suggest this simple outline: Follow-through (review each case from start to finish), Obsolescence (schedule inventories every six months), Control (achieve inventory management by adjusting PAR levels to needs), Utilization (utilize product/equipment with your control), and Standardization (standardize products and measure results).