The following models which provide an estimate of the reliability of a rating scale are described: (1) disattenuation; (2) common factor; (3) external criterion; (4) treatment effects; and (5) regression. Such models are especially useful in selecting, evaluating, and training participants in clinical research. (SLD)

Previous person-fit research is extended through explication of an unexplored model for generating aberrant response patterns. The proposed model is then implemented to investigate the influence of test properties on the aberrancy detection power of a person-fit statistic. Difficulties of aberrancy detection are discussed. (SLD)

A reparameterization of a latent class model is presented to classify and scale nomial and ordered categorical choice data simultaneously. The model extension represents a nonhomogeneous population as a mixture of homogeneous subpopulations. Simulated data and data from a magazine preference survey of 347 college students illustrate the model.…

A method is proposed for calculating the sample size needed to achieve acceptable statistical power with a given test. The minimally important difference significant (MIDS) criterion for sample size is explained and supported with recommendations for determining sample size. The MIDS criterion is computationally simple and easy to explain. (SLD)

Describes a problem formulated by fourth-grade students about having more pizza for lunch, and the clarifying, predicting, modeling, simulating, comparing, and extending activities that occurred in addressing the problem from a probabilistic perspective. (MKR)

Analyzes the properties of genetic sequences that cause the failure of classical algorithms used for data compression. A lossless algorithm, which compresses the information contained in DNA and RNA sequences by detecting regularities such as palindromes, is presented. This algorithm combines substitutional and statistical methods and appears to…

Extensions of unidimensional appropriateness indices are developed for multiunidimensional tests (multidimensional tests composed of unidimensional subtests). Simulated and real data (scores of 2,978 students on the Armed Services Vocational Aptitude Battery) were used to evaluate the indices' effectiveness in determining individuals who are…

W. M. K. Trochim and others defend the record of the regression-discontinuity (RD) design and blur the statistical tests for treatment effect. Their Monte Carlo results show the problematic nature of RD and its potential bias. New testing strategies and restrictions for the application of RD are proposed. (SLD)

The recursive model presented here involves the study of drugs in the bloodstream and their subsequent elimination from the body. Both a basic and a more realistic model are presented and discussed in terms of an algebraic approach, a recursive approach, the graphical representation, and other extensions and connections particularly with models…

The observed probability "p" is the social scientist's primary tool for evaluating the outcome of statistical hypothesis tests. The small-sample accuracy of nonnull asymptotic distributions of several functions of "p" was studied. Implications for use of the approximations are discussed. (SLD)

The reliability of residual scores created in the analysis of covariance in pretest-posttest designs, adjusted for a singe covariate, is compared with that of simple difference scores as relevant parameters vary. Little gain in reliability is created by analysis of covariance, which also suffers from reliability problems. (SLD)

This study reports results of an investigation based on simulated data of the distributional properties of the item fit statistics that are commonly used in the Rasch model calibration programs as indices of the fit of responses to individual items to the measurement model. (SLD)

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)

Modifications are proposed to the recently developed method of comparing one-step M-estimators of location corresponding to two independent groups that provides good control over the probability of Type I error even for unequal sample size, unequal variances, and different shaped distributions. Simulation results reveal cautions required. (SLD)

The extent to which log-linear smoothing could improve the accuracy of common-item equating by the chained equipercentile method in small samples of examinees was investigated with responses from a 100-item test and 93,283 examinees. Smoothing reduced the sample size required for a given degree of accuracy. (SLD)