Response-time models are of increasing interest in educational and psychological testing. This article focuses on the lognormal model for response times, which is one of the most popular response-time models, and suggests a simple person-fit statistic for the model. The distribution of the statistic under the null hypothesis of no misfit is proved…

Response-time models are of increasing interest in educational and psychological testing. This paper focuses on the lognormal model for response times (van der Linden, 2006), which is one of the most popular response-time models, and suggests a simple person-fit statistic for the model. The distribution of the statistic under the null hypothesis…

Being able to characterize the size of raindrops is useful in a number of fields including meteorology, hydrology, agriculture and telecommunications. Associated with this article are data sets containing surface (i.e. ground-level) measurements of raindrop size from two different instruments and two different geographical locations. Students may…

Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This seventh installment of "Explorations in Statistics" explores regression, a technique that estimates the nature of the relationship between two things for which we may only surmise a mechanistic or predictive…

We propose a new limited-information goodness of fit test statistic C[subscript 2] for ordinal IRT models. The construction of the new statistic lies formally between the M[subscript 2] statistic of Maydeu-Olivares and Joe (2006), which utilizes first and second order marginal probabilities, and the M*[subscript 2] statistic of Cai and Hansen…

From a fledgling technology with no proven business models, electronic books (e-books) have grown in importance usurping traditional formats as an acquisitions budget line in many academic library contexts. Business models include purchase, subscription, and pay per use. In academic and research libraries, web based e-book delivery is the dominant…

This article argues that the Normal distribution is often not a good model for anthropomorphic data.

Responds to an earlier article by the same title in Mathematics in School; v25 n2. Asks the question, Which diagram communicates the nature of the distribution most effectively? Uses debate about the number of angels that can balance on a pin head to illustrate various statistical diagrams and explains problems inherent in each. Concludes with…