Comments on some methodological limitations of the research base of "The Bell Curve": blind use of the normal distribution (bell curve); avoidance of nonnormal statistical distributions, which are more appropriate for some social and economic characteristics; copious use of percentiles and quintiles, inappropriate with nonnormal…

A new theoretical analysis of the stop-signal model is proposed. Within the concepts of crude- and net-hazard functions, the nonobservable control-latency distribution can be estimated from observable reaction times. This result allows a test of the Logan and Cowan model (1984) without simplifying assumptions. (SLD)

Reformulates the success-breeds-success (SBS) principle in informetrics in order to generate a general theory of source-item relationships. Topics include a time-dependent probability, a new model for the expected probability that is compared with the SBS principle with exact combinatorial calculations, classical frequency distributions, and…

A modification of Horn's parallel analysis is introduced that is based on the Monte Carlo simulation of the null distributions of the eigenvalues generated from a population correlation identity matrix. This modification reduces the tendency of the parallel analysis procedure to overextract or to extract poorly defined factors. (SLD)

A method is presented for estimating the accuracy and consistency of classifications based on test scores. The reliability of the score is used to estimate effective test length in terms of discrete items. The true-score distribution is estimated by fitting a four-parameter beta model. (SLD)

A method of comparing one-step M-estimates of location for heavy tailed distributions is proposed and investigated. Simulations indicate that the new procedure provides good control over Type I errors and has more power than do some other methods for dealing with heavy tailed distributions. (SLD)

Examines the citation patterns for scientific journal articles and discusses reasons for the skewed distributions of article citedness. Topics discussed include the article age distribution; citations to articles from single journals; citedness of articles written by the same author; possible model distributions of citedness; and citedness as an…

A Monte Carlo simulation explored how to optimize power in the extreme groups strategy when sampling from nonnormal distributions. Results show that the optimum percent for the extreme group selection was approximately the same for all population shapes, except the extremely platykurtic (uniform) distribution. (SLD)

D. W. Zimmerman argues that the interpretation by J. D. Gibbons and S. Chakraborti of recent simulation results and their recommendations are misleading and suggests use of an alternate test when homogeneity of variance and normality are violated. Gibbons and Chakraborti review their differences with Zimmerman's position. (SLD)

Discussion of models for library circulation data highlights a new statistical prediction model that creates a flexible regression curve. Linear graphs that result from previous models are discussed, bivariate discrete distributions are explained, and graphs that show library circulation for one year at a time are presented. (nine references) (LRW)

Illustrates that the Poisson-lognormal model provides good fits to a diverse set of distributions commonly studied in bibliometrics and scientometrics. Topics discussed include applications to the empirical data sets related to the laws of Lotka, Bradford, and Zipf; causal processes that could generate lognormal distributions; and implications for…

Describes a study that was conducted to model the navigation patterns followed by users when retrieving information in hypertext systems. The development of two frequency distribution models is explained, the influence of search tasks on path patterns is discussed, and further research is described. (Contains 17 references.) (LRW)

The adequacy of multidimensional trait and item parameters using multidimensional item response theory analysis was studied through simulation using different degrees of correlation between two trait dimensions and the existence of a restricted trait on the second dimension. Conditions allowing adequate recovery of trait and item parameters are…

The delta method was used to derive standard errors (SES) of the Levine observed score and Levine true score linear test equating methods using data from two test forms. SES derived without the normality assumption and bootstrap SES were very close. The situation with skewed score distributions is also discussed. (SLD)

A flexible class of stochastic mixture models is introduced and illustrated for analysis and interpretation of individual differences in recurrent choice and other types of count data. These models are derived by specifying elements of the choice process at the individual level. An easy-to-implement algorithm is presented for parameter estimation.…