Reports on conditions under which people's probability judgments are superadditive rather than subadditive. Both directions of deviation from additivity are interpreted in a common framework, in which probability judgments are often mediated by judgments of evidence. The two kinds of nonadditivity result from differences in recruitment of…

Six- to 14-year olds added "winning" beads to an urn of "losing" beads in order to generate equal probabilities of choosing a winning bead from each of two urns. Found that 13-year olds integrated the two dimensions (winning and losing beads), the youngest children relied on one dimension, and 9- to 10-year olds partly combined…

Describes similarities and differences between additive conjoint measurement and the Rasch model, and formalizes some new nonparametric item response models that are, in a sense, probabilistic measurement theory models. Applies these new models to published and simulated data. (SLD)

Reports on a study designed to provide baseline data in the area of conjunction and conditional events. Cross-sectional and longitudinal analyses revealed improvement with grade in expressing probability numerically and distinguishing conditional events, but no change in incidence of conjunction errors. (Author/MM)

Compares four methods that map outlier statistics to a familiarity probability scale (a "P" value). Explored these methods in the context of computerized adaptive test data from a 1995 nationally administered computerized examination for professionals in the medical industry. (SLD)

The purpose of this note is to give a construction method for measures of central tendency and dispersion of a set of data on the basis of some symmetric multivariate functions and distance functions. Several examples regarding the known and new measures are presented. (Author/MM)

Statistics are offered to "prove" odds against the origin of life. Presents a summary analysis of all known examples to be used to check these claims whenever they are brought up in conversations, debates, books, or articles. Addresses scientific work misused by anti-evolutionists and the pseudoscientific assertions of the…

Rats obtained food pellets on a variable-interval schedule of reinforcement by nose poking a lighted key. After training to establish baseline performance (with the mean variable interval set at either 60, 120, or 240 s), the rats were given free access to food during the hour just before their daily session. This satiation operation reduced the…

In 1987 the federal government permitted states to raise the speed limit on their rural interstate roads, but not on their urban interstate roads, from 55 mph to 65 mph. Since the states that adopted the higher speed limit must have valued the travel hours they saved more than the fatalities incurred, this institutional change provides an…

The present study was conducted to show how responding in accord with equivalence relations changes as a function of position of familiar stimuli, pictures, and with the use of nonsense syllables in an MTO-training structure. Fifty college students were tested for responding in accord with equivalence in an AB, CB, DB, and EB training structure.…

Mixture models are appropriate for data that arise from a set of qualitatively different subpopulations. In this study, latent class analysis was applied to observational data from a laboratory assessment of infant temperament at four months of age. The EM algorithm was used to fit the models, and the Bayesian method of posterior predictive checks…

In insurance, the analyst is often faced with a large number of inter-related variables for which correlations need to be estimated. Clearly, all correlations lie in the interval [-1, 1], but the numbers cannot be assigned independently. Here, the choices left to the analyst are considered from both a geometric and a probabilistic viewpoint. In…

The national lottery is often portrayed as a game of pure chance with no room for strategy. This misperception seems to stem from the application of probability instead of expectancy considerations, and can be utilized to introduce the statistical concept of expectation.

In this article, we define the inversion vector of a permutation of the integers 1, 2,..., n. We set up a particular kind of permutation, called a partial random permutation. The sum of the elements of the inversion vector of such a permutation is a random variable of interest.

Four experiments are presented that competitively test rule- and exemplar-based models of human categorization behavior. Participants classified stimuli that varied on a unidimensional axis into 2 categories. The stimuli did not consistently belong to a category; instead, they were probabilistically assigned. By manipulating these assignment…