The EM algorithm is used to derive maximum likelihood estimates for item parameters of the two-parameter logistic item response curves. The observed information matrix is then used to approximate the covariance matrix of these estimates. Simulated data are used to compare the estimated and actual item parameters. (Author/BW)

A model is proposed in which the quantification of inverse proportionality is developed beyond the initial qualitative relation. Based on a task analysis, the model was tested with 36 eleven-year-old students in a training experiment using a balance task. (MNS)

The binomial error model includes form-to-form difficulty differences as error variance and leads to Ruder-Richardson formula 21 as an estimate of reliability. If the form-to-form component is removed from the estimate of error variance, the binomial model leads to KR 20 as the reliability estimate. (Author/BW)

Presents a formal model for specification of logical requirements of computer-based information systems that incorporates structural and dynamic aspects based on two separate models: the Logical Information Processing Structure and the Logical Information Processing Network. The model's role in systems development is discussed. (MBR)

Several varieties of perceptual independence are investigated, including sampling independence, dimensional orthogonality, stimulus separability and integrality, and performance parity. A general multivariate perceptual theory is developed, and a precise definition of perceptual independence is offered. (Author/LMO)

Six hundred twenty-six subjects from the University of Arizona participated in an investigation designed to examine congruence of a math domain hierarchy validated psychometrically and validated instructionally. Three studies revealed congruence between hierarchies validated psychometrically and instructionally. Generalization and transfer were…

Structural equation modeling procedures were used to verify a causal relationship between the phonological, word recognition, reading rate, and comprehension components of the reading process. Results indicated proficiency in phonological skills was important for development of word recognition ability, a major contributor to reading…

This paper considers the relation of education and of scientific and technical knowledge developed through research and development to labor productivity growth within the medium term. The empirical significance of sources of productivity growth is tested using data for the United States and 14 other nations. (Author/MLF)

Three different models with continuous materials, discontinuous materials, and number lines were used to study the operation concept in six investigations on multiplication with fractions with pupils aged 11-12 in a Penang International School. All approaches could be understood by pupils, but they preferred the area and fractional models. (MNS)

Describes operations research as an important management tool that can aid library managers in effectively using available resources and as a set of analytical tools that can enable researchers to better understand library and information services. Early history, definition, models, applications to libraries, and impact are noted. Twenty-five…

Applies the confluence model to a longitudinal intact family data set. Also tests the data with simple linear models. Results suggest that the confluence model should be rejected as a useful model for these data based on principles of parsimony and predictability. (Author/AS)

A computer program is presented which simulates the classical probability machine, using Applesoft II high-resolution graphics. Many variables are left to the user's choosing. Suggestions for using the machine, understanding the problem, the mathematical model, and further program documentation are given. (MNS)

Estimation is by means of iterative convergence to maximum likelihood estimates, and two approaches to assessing fit of the model to sample data are discussed. Relation of this general probabilistic model to other, more restricted models is explored and three cases of the general model are applied to exemplary data. (Author/RC)

Context for the application and specialization of a Bayesian linear model is m-group regression and the application to the prediction of grade point average. Specialization involves the assumption of homogeneity of regression coefficients (but not intercepts) across groups. Model's predictive efficiency is compared with that of the full m-group…

The average workweek of full-time workers declined by 35 percent between 1900 and 1940, but has not changed significnatly since then, and the secular rigidity of the full-time workweek remains. An expanded model which incorporates the effects of growth in education and in the female wage explains the post-1940 secular trend. (Editor/HD)