AN EVALUATION OF ORDER RELEASE MECHANISMS IN A JOB-SHOP ENVIRONMENT

Controlling the flow of material on the shop floor involves releasing and dispatching jobs to meet customer due-date requirements while attempting to keep operating costs low. This report presents an evaluation of five releasing mechanisms and four dispatching rules under various levels of aggregate due-date tightness, shop cost structure, and machine utilization using simulation. The performance criteria of total shop cost, jobs on shop floor, deviation from due dates, and job queue time are collected to demonstrate the interactive nature of releasing and dispatching on shop performance.     

IMPLICIT OPTIMAL AND HEURISTIC LABOR STAFFING IN A MULTIOBJECTIVE,MULTILOCATION ENVIRONMENT*

This paper presents a tractable set of integer programming models for the days-off scheduling of a mix of full- and part-time employees working α to β days/week (cycle) in a multiple-objective, multiple-location environment. Previous models were formulated to specifically schedule part-time employees working either two or three days per week. These models were intractable because they required complete employee schedule information. The new models are deemed implicit optimal since they are required to supply only essential information. While the number of variables in previous models is an exponential increasing function of β-α, the size of three of the new models is independent of α and β. The first three models developed here (as in [18]) deal with the trade-offs between idle time, the number of employees required to work at multiple “locations,” and the size of the total labor pool. The inherent flexibility of the implicit modeling approach is illustrated by the presentation of various modifications of the basic models. These modifications permit the use of preference weights on the number of employee work days/week (cycle) or the minimization of payroll costs where differential pay rates exist. These latter models may also be formulated such that idle time is ignored, constrained or minimized. The execution time for the implicit models (on a CDC CYBER 730 computer with commercially available software) averaged well under five seconds on 1200 trial problems for the type of application considered in [18]. A solution was obtained in less than 46 seconds of CPU time for a trial problem which would have required over 1.4 million integer variables with previous models. The availability of optimal solutions was invaluable in the development of two heuristics designed to deal with the trade-offs of [16]. In an experimental analysis a previous heuristic produced results which averaged from 74 to 508 percent above optimum across six experimental conditions. The comparable new heuristic produced results which averaged from 3 to 8 percent above optimum for the same experimental conditions. The paper concludes by developing a framework to integrate the results of this research with the tour scheduling problem and by identifying several other areas for related research.     

THE RELEVANCE OF STATE-UNIVERSITY RETIREMENT PLANS IN JOB SELECTION

Documents provided newly hired faculty members were requested from the major statesupported university in each of the fifty states. Those documents revealed two basic types of retirement plans: (1) state-controlled, defined-benefit plans in which retirement benefits are a function of a formula rather than the contributions by the employee and employer, if any; and (2) third-party, defined-contribution, input-based plans in which the funds are controlled by a third party and the benefits depend upon the amount of contributions and the return earned by them. The analysis focused upon the defined-benefit formula plans and a standard was developed to facilitate analysis. The simulations undertaken reveal significant, decision-relevant biases—especially against faculty who elect to change employers as infrequently as once every ten years when different pension plans are involved! The risks attendant to each type of plan and possible career strategies are discussed.     

PLANNING FOR TRUCK FLEET SIZE IN THE PRESENCE OF A COMMON-CARRIER OPTION

This paper considers a class of network optimization problems in which certain directed arcs must be covered by a set of cycles. Our study was motivated by a distribution planning problem of a commercial firm that had to make deliveries over several origin-destination pairs (directed arcs) and that could service any demand arc by using a vehicle in its own fleet or by paying a common carrier. The problem is to determine an optimal fleet size and the resulting vehicle routes while satisfying maximum route-time restrictions. We formulate the problem, describe some approximate solution strategies, and discuss important implementation issues.     

A COMMENT ON THE COST OF NEW ISSUES OF COMMON STOCK

According to the constant growth model and perceived finance theory, the cost of new external equity exceeds the cost of retained earnings due to flotation costs and underpricing. Carlson and Dietz [1] have recently argued that the constant growth model is operationally inadequate whenever the net proceeds from the issuance of a new share differ from book value. Specifically, they contend that the cost of new external equity is less than the cost of retained earnings whenever the net proceeds from a new share exceed book value. We show that these conclusions stem from an error in interpretation and therefore that the constant growth model is valid regardless of the relationship between market prices and book value.     

LOCATION OF QUALITY INSPECTION STATIONS: AN EXPERIMENTAL ASSESSMENT OF FIVE NORMATIVE HEURISTICS

A number of heuristic decision rules have been proposed to aid in the location of quality inspection stations within a production line. Although these rules apparently enjoy an intuitive appeal, as yet no empirical investigation of their individual efficacies has been undertaken. This research identifies the relations between various cost and/or process characteristics and a designated “operative condition” that motivates the apparent rationale of five of these rules-of-thumb. Experimental results suggest that for several of the heuristics the operative condition was not associated with the performance of the rule. In addition, constraints in the processing environment were found to influence the effectiveness of the heuristics.     

ON THE COST OF NEW ISSUES OF COMMON STOCK: AN AMENDMENT TO THE CONSTANT GROWTH MODEL

Expansion decisions by corporate managements are importantly influenced by their perceptions of the firm's cost of capital and especially the cost of common equity. Their decision making is then influenced by the common perception that new issues of common stock are more costly than retained earnings because of the flotation costs inherent in new issues. Thus a rate of expansion that requires new issues is downgraded in decision making. In this paper the authors show that in actuality new issues of common equity may be less costly than retained earnings. Thus different decision-making implications are clearly involved.     

A UNIFIED APPROACH TO THE PRICE-BREAK ECONOMIC ORDER QUANTITY (EOQ) PROBLEM*

In many developing countries where supply is limited, a premium rather than a discounted price is paid for buying in larger amounts. In order for management science/operations research solutions to be relevant to developing economies, such realities need to be explicitly recognized and any decisions evaluated from that perspective. To illustrate this point, a typical inventory-purchasing problem is solved. In the process, formulae are developed that introduce simultaneous price and quantity sensitivity into the inventory equation. A systematic procedure is suggested to locate the optimal order quantity for a given schedule of discounts or premiums.     

REPLY TO: “ON THE SENSITIVITY OF BRAND-CHOICE SIMULATIONS TO ATTRIBUTE IMPORTANCE WEIGHTS”

Our reply to Curry, Louviere, and Augustine's critique of our earlier paper focuses on differences in motivation between our research and theirs. Our interest in the problem relates to the possible incorporation of self-explicated evaluations in conjoint data collection methods; subsequent to the appearance of our original paper, we have developed hybrid models that combine elements of self-explicated (compositional) and conjoint (decompositional) data collection procedures. As far as we can surmise from their critique, Curry, Louviere, and Augustine are concerned with much broader strategic issues relating share of choices in the consumer population to changes in the shape of attribute weight distributions, shape of the Pareto tradeoff boundary, and so on.     

A COMPARISON OF INVESTMENT ALLOCATION STRATEGIES FOR DISTRIBUTION INVENTORIES

Management goals in distribution inventories are often expressed in terms of the maximum percentage of aggregate sales that should be back ordered. This paper compares several strategies for allocating total inventory investment to each item stocked in order to meet such goals. Computational results are given from a wholesale distribution inventory. The results show that multi-item strategies (which consider the interactions between items) require substantially less investment to meet management goals than strategies that treat each line item independently. All models in this research are approximations based on the assumptions commonly used in practice.     

ESTIMATION OF MISCLASSIFICATION PROBABILITIES IN THE LINEAR PROGRAMMING APPROACHES TO THE TWO-GROUP DISCRIMINANT PROBLEM

Expressions for misclassification probabilities are derived under a contaminated multivariate normal model for the linear-programming approaches to the two-group discriminant problem.     

PROCEDURES FOR DETERMINING RELATIVE FREQUENCIES OF PRODUCTION/ORDER IN MULTISTAGE ASSEMBLY SYSTEMS*

We show that the problems of determination lot sizes in a multistage assembly system for the case of instantaneous production and constant demand for the end item can be reduced to the problems of determining relative frequenceis of production/order for items at each production stage. We further show that such frequencies are independent of the demand levels. Optimal and near-optimal solution procedures for this reduced problem are provided. The near-optimal procedure successively treats each stage of production as a final production stage while simulatenously incorporating decisions made at lower stages into decisions made at higher stages. Experimental results show that the near-optimal procedure results in optimal solutions 75 percent of the time and performs considerably better than representative heuristics available in the literature. Further, its performance is relatively less susceptible to product/structural characteristics of the system.     

THE EFFECTS OF DEGENERACY ON COST-COEFFICIENT RANGES AND AN ALGORITHM TO RESOLVE INTERPRETATION PROBLEMS

The problems of determining valid shadow prices and of performing a valid sensitivity analysis for managerial purposes are considered. For primal degenerate optima, earlier results on finding shadow prices are used to propose a clear and efficient method for finding valid cost-coefficient ranges. An example is used to demonstrate how managerial information can be obtained at degenerate optima.     

THE EFFECT OF ESTIMATION RISK IN PERFORMING STOCHASTIC DOMINANCE EFFICIENCY TESTS

In many applications involving the construction of efficient sets, the parameters of the alternatives are estimated using small examples. As a result, inefficient alternatives may be included in the sample efficient set and efficient alternatives left out. This paper investigates the effects of estimation risk when there are more than two alternatives and limited information. The study reveals that estimation risk is a severe handicap to the practical implementation of stochastic dominance and mean-variance efficiency analysis.     

DESIGNING HIGH-CONTACT SERVICE SYSTEMS: APPLICATION TO BRANCHES OF A SAVINGS AND LOAN*

The customer-contact model represents one of the few conceptually based approaches for designing service systems. This paper develops that concept further for high-contact systems, relative to efficiency and effectiveness notions. Four design features (contact technologies, contact training, data bases, and contact roles) are developed and a simple design methodology (built around the four design features) is presented. A demonstration of the design methodology is provided through its applications to branches of a savings and loan. Areas for additional theoretical and practical refinement of the model and the desirability of multidisciplinary research are discussed.     

MODELING MANAGERS' EFFORT-LEVEL DECISIONS FOR A WITHIN-PERSONS EXAMINATION OF EXPECTANCY THEORY IN A BUDGET SETTING

Ronen and Livingstone [42] have proposed that expectancy theory can provide a unifying framework for accounting research aimed at the motivational impact of budgets on managers. Unfortunately, researchers attempting to use this approach have employed an inappropriate across-persons methodology. This paper uses the decision modeling approach we recently developed [48] to provide a within-persons examination of Vroom's force model in a budget setting. An examination of two hypotheses questions the belief expressed in the budget literature to the effect that the use of currently attainable cost standards results in a cost budget with unique motivating characteristics. Strengths of this research are the use of the within-persons approach and the use of an innovative measure of motivational force.     

SOME STATISTICAL ISSUES IN THE ESTIMATION OF A SIMPLE COST-VOLUME-PROFIT MODEL*

This paper presents point and interval estimators of both long-run and single-period target quantities in a simple cost-volume-profit (C-V-P) model. This model is a stochastic version of the “accountant's break-even chart” where the major component is a semivariable cost function. Although these features suggest obvious possibilities for practical application, a major purpose of this paper is to examine the statistical properties of target quantity estimators in C-V-P analysis. It is shown that point estimators of target quantity are biased and possess no moments of positive order, but are consistent. These properties are also shared by previous break-even models, even when all parameters are assumed known with certainty. After a test for positive variable margins, Fieller's [6] method is used to obtain interval estimators of relevant target quantities. This procedure therefore minimizes possible ambiguities in stochastic break-even analysis (noted by Ekern [3]).