This paper deals with a prey-predator model incorporating a prey refuge and harvesting of the predator species. A mathematical analysis shows that prey refuge plays a crucial role for the survival of the species and that the harvesting effort on the predator may be used as a control to prevent the cyclic behaviour of the system. The optimal…

How common patterns of rater errors may be detected in a large-scale performance assessment setting is discussed. Common rater effects are identified, and a scaling method that can be used to detect them in operational data sets is presented. Simulated data sets are generated to exhibit each of these rater effects. The three continua that depict…

Using computer simulated data, the Type I error rate and statistical power were empirically estimated for several pairwise multiple comparison strategies for situations where population variances differ. Focus was on comparing modified Bonferroni procedures with Dunnett's solutions, and determining whether or not J. P. Shaffer's suggestion of…

The procedure was to isolate the component variables and then to formulate the logical and mathematical rules governing their interaction. Students were classified by age, grade, and sex; also, their entry to, movement through, and graduation from the system were examined. (Author)

Growth curve models are a useful tool for developmentalists because they can estimate an attribute's developmental function by providing a mathematical description of growth on an attribute over time. However, selection of a growth curve model appropriate for estimating individual developmental functions is problematic. The ideal model is the one…

This report contains a theoretical model for describing the motion of a passenger car. The simulation program based on this model is used in conjunction with an advanced driving simulator and run in real time. The mathematical model is complete in the sense that the dynamics of the engine, transmission and steering system is described in some…

The study of the dynamics of physical systems is of importance to all engineering students. LSSP, a Linear System Simulation Program, is used to study the behavior of physical phenomena and systems which may be represented to a good degree of approximation by linear models. Emphasis is placed upon the unity resulting from the mathematical…

This paper examines the effects of learning time on student achievement. It begins by reviewing what is known about how time is allocated and utilized in schools and the effects of differing amounts of exposure to schooling on achievement. Several theoretical perspectives concerning how time spent affects achievement are briefly discussed. The…

As an economical method of evaluating alternative building programs prior to deciding upon one, a computer-based mathematical model is described which could be used to simulate an institution's use of physical facilities. Information is presented regarding program input, measure of effectiveness, and program procedure. Sample forms and sample…

The Airman Training Line Simulator was designed as a managerial aid for investigating and evaluating the various and diverse policy interaction which impact on basic military training and entry-level technical training courses. The user's manual provides user-oriented documentation on the concepts and logic underlying the model. The presentation…

Argues that conventional dynamic modeling techniques divert attention from the importance of model structure and discusses various methods of system representation that are suitable for the analysis and improvement of model structure. (Available from IPC (America) Inc., 205 East 42 Street, New York, NY 10017; $46.80 annually.) (Author/JG)

This research simulated responses of 75 subjects to 30 items under the Birnbaum model and attempted a fit to the data using the Rasch model. When item discriminations varied from a variance of .05 to .25, there was only a slight increase in lack of fit as the variances increased. (Author/CTM)

While it is imperative that attempts be made to assess the predictive accuracy of any prediction model, traditional measures of predictive accuracy have been criticized as suffering from "the base rate problem." The base rate refers to the relative frequency of occurrence of the event being studied in the population of interest, and the…

Some related mathematical models are presented of the bargaining process between an employer, or a group of employers, and a labor union. Its novelty is in the formulation and use of "reactive functions" to explain the attitudes of the respective parties at each stage of the negotiation process and its consequent time-path. (Author)

This article describes how the arrival rate and service time distribution of a queue were investigated, and how a subsequent random-number simulation of the queue was carried out. (MM)