This paper describes a model that integrates an item response theory (IRT) Rasch model and a hierarchical linear model and presents a method of estimating model parameter values that does not rely on large-sample theory and normal approximations. The model resulting from the integration of a hierarchical linear model and the Rasch model allows one…

The feature that makes item response theory (IRT) models the models of choice for many psychometric data analysts is parameter invariance, the equality of item and examinee parameters from different populations. Using the well-known fact that item and examinee parameters are identical only up to a set of linear transformations specific to the…

This paper describes the graded response model. The graded response model represents a family of mathematical models that deal with ordered polytomous categories, such as: (1) letter grading; (2) an attitude survey with "strongly disagree, disagree, agree, and strongly agree" choices; (3) partial credit given in accord with an…

Using abstract models of thesaurus-based and multi-attribute retrieval systems a correspondence between the two systems is established so that equivalent transformation of problem statements expressed by notions developed for one system into problem statements expressed by notions pretaining to the other one may be effectively constructed. (5…

A probabilistic model for interactive retrieval is presented. Bayesian statistical decision theory principles are applied: use of prior and sample information about the relationship of document descriptions to query relevance; maximization of expected value of a utility function, to the problem of optimally restructuring search strategies in an…

The theoretical model of a document retrieval system is described by giving logical meaning to the vagueness and the similarity characteristic to such systems, with the frequency of occurrences of keywords and the relations among them taken into consideration. (6 references) (Author/SJ)

A formula for the ratio of the variance of the pooled transformed data under departure from the binomial assumption to the variance of the pooled transformed data when the binomial assumption holds is given. (Authors)

This paper attempts to analyze the problem of congestion, using a mathematical model shown to be of value in other similar applications. Three criteria of congestion are considered, and it is found that the conclusion one can draw is sensitive to which of these criteria is paramount. (8 references) (Author/NH)

Authors demonstrate that a simple algebraic analysis renders previous interpretations superfluous, making overlap" a tautology and not a hypothesis. (Authors/MB)

A simplified proof of a lemma by Ledermann, which lies at the core of the factor indeterminacy issue, is presented. (Author)

Earlier Analyses are shown to involve special cases of the equations developed here; also that a general four-state chain has the same parameter space as an all-or-none model if and only if its representation with an observable absorbing state is lumpable into a Markov chain with three states. (Author/GS)

Presents a model for the removal of ozone from air masses by vegetation. Compares simulation with Los Angeles data, and suggests needed research. (AL)

The authors, members of a group that has been studying university planning since 1965, describe a mathematical, computerized model of university activities which they are now constructing, using data from the University of Reading. (JW)