This paper analyzes some of the problems of using diffusion models to formulate marketing strategies for new products. Though future work in this area appears justified, many unresolved problems limit its application. There is no theory for adoption and diffusion processes; such a theory is outlined in this paper. The present models are too…

In this paper, a heuristic algorithm for constructing school timetables is described. The algorithm is based on an exact method that applies to a family of particular timetable problems. The procedure has been used to construct timetables for Swiss schools having about 50 classes, 80 teachers, and 35 weekly periods. Less than five percent of…

The document covers an operational entity-simulation system designed to permit observation and selective control of a military personnel system under a variety of policy alternatives. PERSYM is modularized to facilitate conversion to different military forces and the programing and inclusion of alternative policy logic modules. The system…

A study was made of the problem of representing the expectations of mean squares associated with analysis of variance sources of variation for experimental designs. These designs have a factorial structure over repeated measures or, for some other reason, have variates within a factorial design not all of which are mutually independent. A simple…

Three different strategies of choosing items for presentation in a simple list learning situation are compared. The instructional task was to teach the correct response to a number of stimulus items, using a paired-associate teaching procedure. Only one item could be presented on a given trial and the total number of trials was limited. The…

Multiple matrix sampling is a psychometric procedure in which a set of test items is subdivided randomly into subtests of items with each subtest administered to different subgroups of examinees selected at random from the examinee population. Although each examinee receives only a proportion of the complete set of items, the statistical model…

The question of whether a library's catalog should consist of cards arranged in a single alphabetical order (the "dictionary catalog) or be segregated as a separate file is discussed. Development is extended to encompass related problems involved in the creation of a book catalog. A model to study the effects of congestion at the catalog is…

To resolve a recent controversy between Klein and Cleary and Levy, a model for dichotomous congeneric items is presented which has mean errors of zero, dichotomous true scores that are uncorrelated with errors, and errors that are mutually uncorrelated. (Author)

Explicit formulas are derived for the asymptotic sampling variances and covariances of the maximum likelihood estimators for factor-analysis parameters in the special case where there is just one common factor. The effect of the number of variables on these variances and covariances is indicated. A formula is given showing to what extent the usual…

A general computer program for estimating the unknown coefficients in a set of linear structural equations is described. In its most general form, the variables in the equation system may be unmeasured hypothetical constructs or latent variables, and there may be several measured variables or multiple indicators for each unmeasured variable. Also,…

The 50 papers on educational evaluation presented at the 1972 AERA Conference are reviewed. The papers were classified into four categories: Theory and Methodology, Empirical Models, Empirical Studies, and Nationwide Evaluation and State Assessment. A list of the papers reviewed, their authors, and, when applicable, the ED numbers concludes the…

The effects of dynamic quantum allocation and swap-time variability on central processing unit (CPU) behavior are investigated using a model that allows both quantum length and swap-time to be state-dependent random variables. Effective CPU utilization is defined to be the proportion of a CPU busy period that is devoted to program processing, i.e.…

Two specific approaches of how to evaluate an information retrieval system are explored. The first is a mathematical model for use in studying how to minimize operating costs. The model provides a method for comparative evaluation between systems. The cost model divides the costs of a retrieval system into two components: system costs and user…

Several different mathematical methods for optimization of instruction are presented and compared. A way in which one of these methods might be applied to the measurement and avoidance of inequality in educational opportunity and performance is presented. Finally, it is suggested that computer-assisted instruction might provide a particularly…

Designed for the student of urban simulation, this paper offers definitions of "models"--conceptual or mathematics formulations of concrete things or of abstract relations between them--and of "simulation"--an act or process, conducted either by persons or devices, by which a model or a hierarchy of models is made to imitate reality. Six basic…