A Multiple-community Overlap Measure Based on a Probabilistic Approach

Species diversity indices are designed to measure the species diversity of a community and to compare the species distribution structure of two communities. The Shannon and Simpson indices are for describing one community, and the Jaccard and Morisita indices are for comparing two communities. Only a few indices allow the simultaneous comparison of three or more communities. In this study, we propose a multiple-community similarity index based on a probabilistic approach, and compare it with other multiple-community indices. Empirical examples are considered as a demonstration of the proposed similarity indices.     

The Use of Investigations in the Introductory Statistics Course

Reasons for including investigations in a first course in statistics are presented. Investigations create an environment of participation and give the student the opportunity to experience statistics in action. This participation highlights the interaction between science and statistics. Suggestions are made regarding the integration of investigations into a formal course environment. One investigation is presented in detail. Thirteen other investigations are outlined. Emphasis is placed on experiments that require minimal set-up time yet illustrate important statistical concepts.     

Analogies for Helping Clinicians and Investigators Better Understand the Principles and Practice of Biostatistics

For the interaction between the biostatistician and the clinician or research investigator to be successful, it is important not only for the investigator to be able to explain biological and medical principles in a way that can be understood by the biostatistician, so, too, the biostatistician needs tools to help the investigator understand both the practice of statistics and specific statistical methods. In our practice, we have found it useful to draw analogies between statistical concepts and familiar medical or everyday ideas. These analogies help to stress a point or provide an understanding on the part of the investigator. For example, explaining the reason for using a nonparametric procedure (a general procedure used when the underlying distribution of the data is not known or cannot be assumed) by comparing it to using broad spectrum antibiotics (a general antibiotic used when the specific bacteria causing infection is unknown or cannot be assumed) can be an effective teaching tool. We present a variety of useful (and hopefully amusing) analogies that can be adopted by statisticians to help investigators at all levels of experience better understand principles and practice of statistics.     

Identifying non-competitive bids in construction contract auctions

Construction contract auctions are characterised by (1) anticipated high outliers due to the presence of non-competitive bids, (2) very small samples and (3) uncertainty of the appropriate underlying density function model of the bids. This paper describes the simultaneous identification of high outliers and density function by systematically identifying and removing candidate (high) outliers and examining the composite goodness-of-fit of the resulting reduced samples with the normal and lognormal density functions. Six different identification strategies are tested empirically by application, both independently and in pooled form, to several sets of auction data gathered from around the world. The results indicate the normal density to be the most appropriate model and a multiple of the auction standard deviation to be the best identification strategy.     

Online algorithms for maximizing weighted throughput of unit jobs with temperature constraints

We consider a temperature-aware online deadline scheduling model. The objective is to schedule a number of unit jobs, with release dates, deadlines, weights and heat contributions, to maximize the weighted throughput subject to a temperature threshold. We first give an optimally competitive randomized algorithm. Then we give a constant competitive randomized algorithm that allows a tradeoff between the maximum heat contribution of jobs and the competitiveness. Finally we consider the multiple processor case and give several tight upper and lower bounds.     

Corporate prediction markets: a tool for predicting market shares

Prediction markets have been applied for various forecasting issues, such as political events or sports. The ability of these markets to collect distributed information in a fast and efficient way provides useful support for corporate planning. A crucial criterion for the quality of the information aggregation process is the liquidity of the market, especially in corporate prediction markets, which typically consist of fewer traders than public markets. The use of automated market makers is one option with which to ensure enough liquidity, but it is always related to some drawbacks. This paper investigates a field study of a corporate prediction market that replaces the automated market maker with human traders. We analyze the efficiency of such markets, the impact of the applied incentive system and the effects of human market makers.     

The benefits of a nap during prolonged work and wakefulness

Abstract

Prolonged work scenarios with demands for sustained performance are increasingly common. Because sleep loss inevitably compromises functioning in such situations, napping has been proposed as a countermeasure. The optimal timing of the nap relative to its benefits for performance and mood is not known, however. To address this issue, 41 healthy adults were permitted a two-hour nap at one of five times during a 56-hour period of intermittent work, with no other sleep. Naps were placed 12 hours apart, near the circadian peak (P) or trough (T), and were preceded by 6(P), 18(T), 30(P), 42(T), or 54(P) hours of wakefulness. Work test bouts occurred every few hours and consisted of a variety of psychomotor and cognitive tasks as well as mood scales completed at the beginning, middle and end of each bout. A total of eight performance and 24 mood parameters were derived from the bouts and compared between groups at all test points prior to and following the naps. An estimate of the extent to which each nap condition differed from the control (P54) condition was derived by totalling the proportion of test points that yielded statistically significant results relative to the total number of tests conducted both before and after naps.

Although all performance and most mood parameters displayed a circadian-modulated deterioration as the protocol progressed, a nap appeared to attentuate the extent of this change in all performance parameters but not in mood parameters. Overall, the timing of the nap across days and within the circadian cycle was irrelevant to its effect on performance, suggesting that it diminished the intrusion of sleepiness into behavioural functioning, even though subjects were phenomenally unaware of this benefit.     

Developmental stability and leadership effectiveness

Developmental stability is the degree to which we can withstand environmental or genetic stressors during development. Fluctuating asymmetry (FA), concerns the extent to which the right and left side of the body is asymmetrical and is one way to measure developmental stability. Two studies were carried out that examined both the predictive value of leader FA with leadership behaviors and its role in facilitating group performance. The first study examined the hypothesis that a leader's FA is correlated with scores on the Multifactor Leadership Questionnaire (MLQ). The results revealed individuals with a more asymmetrical morphology scored higher on the transformational, but not transactional, dimensions of leadership behavior. A second study examined the hypothesis that asymmetrical morphology and leadership effectiveness would share a positive relationship. In this study participants who led a business game exercise, revealed a positive relationship between FA and self-reported well-being and task satisfaction. Importantly, there was also a positive correlation between the leader's FA score and group performance. The role that developmental stability may play in leadership effectiveness is discussed in the wider context of evolutionary psychology.     

Workload Control and Order Release: A Lean Solution for Make‐to‐Order Companies

Protecting throughput from variance is the key to achieving lean. Workload control (WLC) accomplishes this in complex make‐to‐order job shops by controlling lead times, capacity, and work‐in‐process (WIP). However, the concept has been dismissed by many authors who believe its order release mechanism reduces the effectiveness of shop floor dispatching and increases work center idleness, thereby also increasing job tardiness results. We show that these problems have been overcome. A WLC order release method known as “LUMS OR” (Lancaster University Management School order release) combines continuous with periodic release, allowing the release of work to be triggered between periodic releases if a work center is starving. This paper refines the method based on the literature (creating “LUMS COR” [Lancaster University Management School corrected order release]) before comparing its performance against the best‐performing purely periodic and continuous release rules across a range of flow directions, from the pure job shop to the general flow shop. Results demonstrate that LUMS COR and the continuous WLC release methods consistently outperform purely periodic release and Constant WIP. LUMS COR is considered the best solution in practice due to its excellent performance and ease of implementation. Findings have significant implications for research and practice: throughput times and job tardiness results can be improved simultaneously and order release and dispatching rules can complement each other. Thus, WLC represents an effective means of implementing lean principles in a make‐to‐order context.