A solution of the convection-dispersion equation is used to describe the solute breakthrough curves generated in the demonstrations in the companion paper. Estimation of the best fit model parameters (solute velocity, dispersion, and retardation) is illustrated using the method of moments for an example data set. (Author/MDH)

Presents simple experiments using the flow of water from bell jars that can provide an easily visualized introduction to exponential decay. (Author)

Although two-stage testing is not the most efficient form of adaptive testing, it has some advantages. In this paper, linear programming models are given for the construction of two-stage tests. In these models, practical constraints with respect to, among other things, test composition, administration time, and inter-item dependencies play an…

This set of transparencies shows how the manipulation of combinatorial structures in the context of modern combinatorics can easily lead to interesting teaching and learning activities at every level of education from elementary school to university. The transparencies describe: (1) the importance and relations of combinatorics to science and…

Discussed is the virial theorem, which is useful in classical, quantum, and statistical mechanics. Two types of derivations of this theorem are presented and the relationship between the two is explored. (BT)

Discusses the use of mathematical modeling. Describes types, examples, and importance of mathematical models. (YP)

Describes the use of step-functions in modelling instruction. Classifies modelling into three categories: direct, analogical, and creative application. Provides and discusses modelling postal rates and other problems as examples. (YP)

Identifies a set of objects that is genuinely indigenous to management information systems and constructs a simple model based on them. The model's four basic entities, which define the scope of information theory, are data, information, knowledge, and wisdom. (Contains 46 references.) (KRN)

Discusses a misconception about the cycloid that asserts the final point on the path of shortest time in the "Brachistochrone" problem is at the lowest point on the cycloid. Uses a BASIC program for Newton's method to determine the correct least-time cycloid. (MDH)

Direct and indirect effects in decomposed zero-order correlations among variables in causal models are considered. Under certain circumstances, the components of the decompositions could be interpreted as direct, indirect, and spurious causal effects, plus a component called joint associations. The sum of the direct and indirect effects is the…

Describes the spectrum of process design problems. Suggests a methodology for teaching some concepts used in design, including the types of processes considered and their designs, new tools useful in conceptual design, and a strategy for developing conceptual designs. (YP)

The purpose of this article is to describe a middle school mathematics teacher's model of his students' responses to algebraic tasks involving equivalent expressions and the distributive property. The teacher engaged in two model-eliciting activities designed for teachers by creating a library of his students' work and an accompanying "Ways…

The Feldt-Gilmer congeneric reliability coefficients make it possible to estimate the reliability of a test composed of parts of unequal, unknown length. The approximate standard errors of the Feldt-Gilmer coefficients are derived via a method using the multivariate Taylor's expansion. Monte Carlo simulation is employed to corroborate the…

In all latent trait models there is an equation which describes the probabilistic outcome of the interaction of a person with a known ability and an item with a known difficulty. This modeled outcome can be compared to the observed outcome, and the residuals can be summed over the items to assess the fit of the person to the model. Various…

A general procedure is presented for generating code values for a qualitative variable in multiple linear regression analyses that result in directly interpretable estimates of interest. The basic approach, in viewing ANOVA as a multiple regression problem, is to derive quantitative code values for the various levels of the qualitative ANOVA…