Statistical Power in Operations Management Research

This paper discusses the need and importance of statistical power analysis in field-based empirical research in Production and Operations Management (POM) and related disciplines. The concept of statistical power analysis is explained in detail and its relevance in designing and conducting empirical experiments is discussed. Statistical power reflects the degree to which differences in sample data in a statistical test can be detected. A high power is required to reduce the probability of failing to detect an effect when it is present. This paper also examines the relationship between statistical power, significance level, sample size and effect size. A probability tree analysis further explains the importance of statistical power by showing the relationship between Type 11 errors and the probability of making wrong decisions in statistical analysis. A power analysis of 28 articles (524 statistical tests) in the Journal of Operations Management and in Decision Sciences shows that 60% of empirical studies do not have high power levels. This means that several of these tests will have a low degree of repeatability. This and other similar issues involving statistical power will become increasingly important as empirical studies in POM study relatively smaller effects

Service Capacity Design With an Integrated Market Utility-Based Method

[Excerpt] The purpose of this chapter is to present a model that integrates customer preferences and service design. In response to the need for interdisciplinary service management research, we present a framework that specifies the key elements of an integrated market utility-based model (MUM) and a method for determining optimal service designs based on customer needs and preferences. We also explore the relationships among revenue, capacity costs, and those service design attributes that have significant operational consequences. Our model builds on the topics we have described and integrates customer utility models that are commonly used in market research with capacity variables and their corresponding costs that are typical operations management issues. The proposed method is general and can be adapted for different types of service operations

A Market-Utility Approach to Scheduling Employees

[Excerpt] Scheduling front-line service providers is a constant challenge for hospitality managers, given the inevitable tradeoff between service standards and operating expense. Traditional employee scheduling typically applies a cost-minimization approach to specify the level of front-line service providers who will be available to meet periodic demand. That cost includes the opportunity cost of lost customers, which is part of the pseudo-costs of understaffing. A confounding and often ignored effect, however, is the benefit generated by maintaining high service levels in a system where capacity exceeds demand. That is, scheduling more frontline service providers than the minimum level necessary to provide acceptable customer service (what might be considered to be overstaffing in some rubrics) may mean that customers receive service that is better than they expected (or what company standards prescribe). In this paper we report on a scheduling approach that explicitly considers the interrelationships among customer preferences, customer demand, waiting times, and scheduling decisions. This approach, which we call the market-utility model for scheduling (MUMS), helps managers consider the dynamics of scheduling service employees. First, we discuss the components that make up this approach, which includes methods from customer-preferences modeling, service-capacity planning, and the four tasks of labor scheduling proposed by Thompson. Next, we\u27ll show how the model applies to balancing queue lengths and operating costs for an airport food-court vendor. Finally, we discuss the value of MUMS for hospitality managers

A Market Utility-Based Model for Capacity Scheduling in Mass Services

Only a small set of employee scheduling articles have considered an objective of profit or contribution maximization, as opposed to the traditional objective of cost (including opportunity costs) minimization. In this article, we present one such formulation that is a market utility-based model for planning and scheduling in mass services (mums), mums is a holistic approach to market-based service capacity scheduling. The mums framework provides the structure for modeling the consequences of aligning competitive priorities and service attributes with an element of the firm’s service infrastructure. We developed a new linear programming formulation for the shifts-scheduling problem that uses market share information generated by customer preferences for service attributes. The shift-scheduling formulation within the framework of mums provides a business-level model that predicts the economic impact of the employee schedule. We illustrated the shift-scheduling model with empirical data, and then compared its results with models using service standard and productivity standard approaches. The result of the empirical analysis provides further justification for the development of the market-based approach. Last, we discuss implications of this methodology for future research

Designing and Positioning Food Services for Multicultural Markets

[Excerpt] Businesses that seek to develop an appropriate operations strategy for serving a multicultural customer market face challenges that are distinct from businesses that serve a relatively homogeneous local market. While the strategic implications of expanding services from a domestic market to international locations have been well documented, the issue of dealing with multinational customers at a single location has largely been neglected by researchers, as far as we can determine. This paper attempts to fill the research gap by presenting a method for determining the extent to which restaurant managers should maintain standard menus and food items, as opposed to customizing their operations for different ethnic and cultural groups. To that end, we applied a customer-based approach to help managers at four international-airport food outlets to improve their food- service revenues from their three major passenger groups: English-, Japanese-, and Spanish-speaking customers. In this case, language preference was used as a proxy for cultural identity. We submit that although there are many differences among, say, English-speaking peoples, they are more similar to each other than they are to, say, Spanish speakers. Moreover, the language a person speaks is a substantial factor in trying to communicate in a particular location. One can guess that Japanese speakers in the United States, for example, might experience more language barriers than either English or Spanish speakers. We present an approach for modeling the preferences of different cultural groups, evaluating the differences among the groups, and determining a strategy to maximize market share for each of the four food-service providers that we studied. Indeed, one food-service vendor implemented our study\u27s recommendations and enjoyed a substantial revenue gain over the previous year\u27s same-period sales. We believe that the method we propose has valuable implications for any service provider who must consider operating strategies for a multicultural or multinational site, although we focus on the distinct concept of a domestic foodservice business that serves a multicultural market

Labor scheduling with employee turnover and absenteeism

Most labor staffing and scheduling models presume that all employees scheduled for duty reliably report for work at the beginning of their shift. For industries with even moderate turnover or absenteeism, this assumption may be quite costly. We present a profit-oriented labor scheduling model that accounts for the day-to-day flux of employees and capacity induced by voluntary resignations, new hires, experience curves, and absenteeism. The proposed model also anticipates revenue losses due to reneging by customers whose patience decays exponentially with queue time. Our computational studies suggest that firms with comparatively high transaction volumes, long transaction times, and/or relatively tight profit margins may experience significant benefit from this approach. Compared with conventional labor scheduling models, the proposed method boosts average expected profits by more than 10 percent in certain operating environments

Research Opportunities in Service Process Design

This paper presents an overview of the new issues and research opportunities related to four service operations design topics—the design of retail and e-tail service processes, design of service processes involving waiting lines and workforce staffing, service design for manufacturing, and re-engineering service processes. All four topics are motivated by new technologies (particularly web-based technologies) and require a multi-disciplinary approach to research. For each topic, the paper presents an overview of the topic, the relevant frameworks, and a discussion of the research opportunities

Properties of the Volume Operator in Loop Quantum Gravity II: Detailed Presentation

The properties of the Volume operator in Loop Quantum Gravity, as constructed by Ashtekar and Lewandowski, are analyzed for the first time at generic vertices of valence greater than four. The present analysis benefits from the general simplified formula for matrix elements of the Volume operator derived in gr-qc/0405060, making it feasible to implement it on a computer as a matrix which is then diagonalized numerically. The resulting eigenvalues serve as a database to investigate the spectral properties of the volume operator. Analytical results on the spectrum at 4-valent vertices are included. This is a companion paper to arXiv:0706.0469, providing details of the analysis presented there.Comment: Companion to arXiv:0706.0469. Version as published in CQG in 2008. More compact presentation. Sign factor combinatorics now much better understood in context of oriented matroids, see arXiv:1003.2348, where also important remarks given regarding sigma configurations. Subsequent computations revealed some minor errors, which do not change qualitative results but modify some numbers presented her

Rereading the Universal Declaration of Human Rights: plurality and contestation, not consensus

In this paper I examine the drafting of the Universal Declaration of Human Rights. My analysis counters conventional narratives of consensus and imposition that characterize the development of the UN human rights regime. The central argument is that within the founding text of the contemporary human rights movement there is an ambiguous account of rights, which exceeds easy categorization of international rights as universal moral principles or merely an ideological imposition by liberal powers. Acknowledging this ambiguous history, I argue, opens the way to an understanding of human rights as an ongoing politics, a contestation over the terms of legitimate political authority and the meaning of “humanity” as a political identity