A situation in which shoppers are waiting in supermarket check-out lines is simulated to determine an optimum number of check-outs using data on the number of shoppers and the serving time. (MN)

An example of a mathematical modeling problem involving student enrollment and attrition is given along with a discussion of methods and conclusions. (MN)

An example is given of a mathematical modeling problem involving the number of people that get on and off an elevator and the expected number of stops it makes. (MN)

The author presents an approach to the teaching of undergraduate introductory probability and statistics. He also presents experimental evidence that suggests the approach helps students rely upon probability theory in making estimates for the likelihood of events rather than rely upon heuristic principles which may bias probability estimates. (MN)

A properly chosen test model defines the kind of dependence of the observable behavior on underlying abilities of the persons tested in the form of a data-adequate theory. The limitations and potential of several test models are detailed; and they are critically compared as an aspect of empirical evaluation. (Author/MV)

Statements made in a previous article of this journal concerning the Rasch latent trait test model are questioned. Methods of estimation, necessary sample sizes, several formuli, and the general usefulness of the Rasch model are discussed. (JKS)

Using the assumption of randomly parallel tests and concepts from generalizability theory, three signal/noise ratios for domain-referenced tests are developed, discussed, and compared. The three ratios have the same noise but different signals depending upon the kind of decision to be made as a result of measurement. (Author/JKS)

The principles of modern genetics are extended to study the extinction probabilities of such genetic diseases as sickle-cell anemia, Tay-Sachs disease, and cystic fibrosis. (JT)

A manipulative model for the addition, subtraction, and multiplication of integers is described in which a carpet square with a hole in it and the plug that fits in the hole are "opposites" of each other. Several other models for integer multiplication are briefly described. (MN)

Described is the development of a simulation, or model of an existing congested pedestrian crossing situation by elementary school students in order to conduct trials of their solutions. (MN)

Applies the Box-Jenkins time series methodology to enrollment data for the Virginia community college system. Describes the enrollment data set, the Box-Jenkins approach, and the forecasting results. Discusses the value of one-quarter ahead enrollment forecasts and implications for practice. Provides a technical discussion of the model. (DMM)

Partial knowledge was assessed in a multiple choice vocabulary test. Test reliability and concurrent validity were compared using Rasch-based dichotomous and polychotomous scoring models. Results supported the polychtomous scoring model, and moderately supported J. O'Connor's theory of vocabulary acquisition. (Author/GDC)

The rule space model permits measurement of cognitive skill acquisition and error diagnosis. Further discussion introduces Bayesian hypothesis testing and bug distribution. An illustration involves an artificial intelligence approach to testing fractions and arithmetic. (Author/GDC)

There are many problems that can be translated into the language of graph theory. Such a problem, discussed in this article is to show that in any group of two or more people, there are at least two people who have the same number of acquaintances in the group. (PK)

This special issues describes multidimensional scaling (MDS), with emphasis on proximity and preference models. An introduction and six papers review statistical developments in MDS study design and scrutinize MDS research in four areas of application (consumer, social, cognitive, and vocational psychology). (SLD)