One of the major theoretical and practical developments in testing is latent trait analysis and item response theory. This report provides a guide for practitioners in understanding, evaluating, and using these developments to meet their testing needs. (Author)

The "positive-negative charge" model is described and demonstrated with all four operations on integers. Its major advantages are that it is both concrete and complete. (MNS)

Typically, nonlinear models such as those used in the analysis of covariance structures, are not globally identifiable. Investigations of local identifiability must either yield a mapping onto the entire parameter space, or be confined to points of special interest such as the maximum likelihood point. (Author/JKS)

A theory for storage and retrieval of associative information is presented. Items or events are represented as random vectors. Convolution is used as the storage operation, correlation as the retrieval operation. A distributed memory system is assumed. The theory applies to recognition and recall and covers both accuracy and latency. (Author/RD)

A linear structural model for comparing quasi-Markov models across populations is demonstrated. A confirmatory factor analysis formulation of the simplex model is also developed for between group comparisons. A variety of possible applications of this approach are suggested. (Author)

The use of segmented polynomial models is explained. Examples of design matrices of dummy variables are given for the least squares analyses of time series and discontinuity quasi-experimental research designs. Linear combinations of dummy variable vectors appear to provide tests of effects in the two quasi-experimental designs. (Author/BW)

A general model for prediction and association is described for the situation in which both criterion and predictor(s) are discrete variables. The approach can be employed for the general case involving any number of predictors, and the related measures of multiple and partial association are described. (Author/GK)

A method based on the likelihood ratio procedure is presented for use in selecting a measurement model from among the Rasch, two-parameter, and three-parameter logistic latent trait models. (Author/BW)