Stochastics and Statistics Joint economic design of EWMA control charts for mean and variance

Abstract Control charts with exponentially weighted moving average (EWMA) statistics (mean and variance) are used to jointly monitor the mean and variance of a process. An EWMA cost minimization model is presented to design the joint control scheme based on pure economic or both economic and statistical performance criteria. The pure economic model is extended to the economic-statistical design by adding constraints associated with in-control and out-of-control average run lengths. The quality related production costs are calculated using Taguchi's quadratic loss function. The optimal values of smoothing constants, sampling interval, sample size, and control chart limits are determined by using a numerical search method. The average run length of the control scheme is computed by using the Markov chain approach. Computational study indicates that optimal sample sizes decrease as the magnitudes of shifts in mean and/or variance increase, and higher values of quality loss coefficient lead to shorter sampling intervals. The sensitivity analysis results regarding the effects of various inputs on the chart parameters provide useful guidelines for designing an EWMA-based process control scheme when there exists an assignable cause generating concurrent changes in process mean and variance

Developing limits for driving under cannabis

ABSTRACT Objective Development of a rational and enforceable basis for controlling the impact of cannabis use on traffic safety. Methods An international working group of experts on issues related to drug use and traffic safety evaluated evidence from experimental and epidemiological research and discussed potential approaches to developing per se limits for cannabis. Results In analogy to alcohol, finite (non-zero) per se limits for delta-9-tetrahydrocannabinol (THC) in blood appear to be the most effective approach to separating drivers who are impaired by cannabis use from those who are no longer under the influence. Limited epidemiological studies indicate that serum concentrations of THC below 10 ng/ml are not associated with an elevated accident risk. A comparison of meta-analyses of experimental studies on the impairment of driving-relevant skills by alcohol or cannabis suggests that a THC concentration in the serum of 7-10 ng/ml is correlated with an impairment comparable to that caused by a blood alcohol concentration (BAC) of 0.05%. Thus, a suitable numerical limit for THC in serum may fall in that range. Conclusions This analysis offers an empirical basis for a per se limit for THC that allows identification of drivers impaired by cannabis. The limited epidemiological data render this limit preliminary

Understanding sweet-liking phenotypes and their implications for obesity: narrative review and future directions

Building on a series of recent studies that challenge the universality of sweet liking, here we review the evidence for multiple sweet-liking phenotypes which strongly suggest, humans fall into three hedonic response patterns: extreme sweet likers (ESL), where liking increases with sweetness, moderate sweet likers (MSL), who like moderate but not intense sweetness, and sweet dislikers (SD), who show increasing aversion as sweetness increases. This review contrasts how these phenotypes differ in body size and composition, dietary intake and behavioural measures to test the widely held view that sweet liking may be a key driver of obesity. Apart from increased consumption of sugar-sweetened beverages in ESL, we found no clear evidence that sweet liking was associated with obesity and actually found some evidence that SD, rather than ESL, may have slightly higher body fat. We conclude that ESL may have heightened awareness of internal appetite cues that could protect against overconsumption and increased sensitivity to wider reward. We note many gaps in knowledge and the need for future studies to contrast these phenotypes in terms of genetics, neural processing of reward and broader measures of behaviour. There is also the need for more extensive longitudinal studies to determine the extent to which these phenotypes are modified by exposure to sweet stimuli in the context of the obesogenic environment

A História da Alimentação: balizas historiográficas

Os M. pretenderam traçar um quadro da História da Alimentação, não como um novo ramo epistemológico da disciplina, mas como um campo em desenvolvimento de práticas e atividades especializadas, incluindo pesquisa, formação, publicações, associações, encontros acadêmicos, etc. Um breve relato das condições em que tal campo se assentou faz-se preceder de um panorama dos estudos de alimentação e temas correia tos, em geral, segundo cinco abardagens Ia biológica, a econômica, a social, a cultural e a filosófica!, assim como da identificação das contribuições mais relevantes da Antropologia, Arqueologia, Sociologia e Geografia. A fim de comentar a multiforme e volumosa bibliografia histórica, foi ela organizada segundo critérios morfológicos. A seguir, alguns tópicos importantes mereceram tratamento à parte: a fome, o alimento e o domínio religioso, as descobertas européias e a difusão mundial de alimentos, gosto e gastronomia. O artigo se encerra com um rápido balanço crítico da historiografia brasileira sobre o tema

Global Production Planning under Exchange-Rate Uncertainty

Motivated by a production planning problem in an actual global manufacturing network, we examine the impact of exchange-rate uncertainty ... namely the volatility in and correlations among exchange rates ... on the choice of various optimal production policies and the conditions which lead to them. A two-stage stochastic program with recourse is developed that provides opportunities to hedge financial risk by allowing for some production planning decisions to be deferred until exchange rates are realized. The proposed model and analysis yield the following results: (1) Under significant exchange-rate uncertainty it may be optimal to hedge production by producing less than total demand, (2) production hedging is more likely an optimal policy when either the profit margin is small and/or the exchange rates are highly volatile, (3) the probability of following a production hedging policy decreases as the correlations between exchange rates monotonically increase in a positive direction, (4) after exchange rates are realized it may be optimal to hedge allocation by not allocating all production to some of the markets, and (5) given production and/or allocation hedging, our model identifies the value of financial hedging for each firm rather than a single option price for all firms. This guarantees that all markets are served and that each firm gets an option price that is commensurate with its exchange-rate risk. These findings and implications are illustrated with examples adapted from data provided by IBM

An Experimental Investigation of Decision Making in a Simulated Research and Development Environment

Information processing and choice behavior of research and development (R&D) managers and MBA students were investigated through play of a simple R&D decision game under conditions of technical uncertainty. The experimental design permitted a detailed micro-analysis of the players' behavior. The research data were collected in concert with the game's use as a training vehicle, which also permitted exploration of improved methods for effectively educating practitioners in these concepts and the assessment of the potential imposition of decision theory on managerial decision making. The rules deduced describing information processing and decision processes have important implications for training in decision theory. Significant differences in game behavior were found between R&D managers and students. The significant degree of irrational and suboptimal behavior exhibited, the R&D managers' willingness to accept the norms of decision theory as a basis of rational thought, and their general interest in the topic of decision making underscore the importance of educating managers in the concepts of decision theory.

Regression models of behavior for managerial decision making

A principal problem in systems studies concerns the development of models that will be accepted and used by decision makers in organizations. Regression models derived from managers' past behavior offer promise in overcoming this problem for many repetitive types of decisions. Employing a simulated production planning environment, this paper discusses both the potential usefulness and limitations of such models for understanding and improving decision making in practical applications.