Researchers who work with ordinal rating scales sometimes encounter situations where the scale categories do not function in the intended or expected way. For example, participants' use of scale categories may result in an empirical difficulty ordering for the categories that does not match what was intended. Likewise, the level of distinction…

The purpose of this study is to illustrate the use of functional data analysis (FDA) as a general methodology for analyzing person response functions (PRFs). Applications of FDA to psychometrics have included the estimation of item response functions and latent distributions, as well as differential item functioning. Although FDA has been…

Rater fit analyses provide insight into the degree to which rater judgments correspond to expected properties, as defined within a measurement framework. Parametric models such as the Rasch model provide a useful framework for evaluating rating quality; however, these models are not appropriate for all assessment contexts. The purpose of this…

Cognitive diagnosis models (CDMs) have gained increasing popularity recently because of their potential to provide diagnostic inferences that can inform learning and teaching. However, the development of cognitive diagnostic assessments (CDAs) is lagging behind the development of the associated psychometric models. At present, it is not clear…

The R software provides packages and functions that provide data analysis in classical true score, generalizability theory, item response theory, and Rasch measurement theories. A brief list of notable articles in each measurement theory and the first measurement journals is followed by a list of R psychometric software packages. Each psychometric…

The "extended Rasch modeling" (eRm) package in R provides users with a comprehensive set of tools for Rasch modeling for scale evaluation and general modeling. We provide a brief introduction to Rasch modeling followed by a review of literature that utilizes the eRm package. Then, the key features of the eRm package for scale evaluation…

In his focus article, "Rethinking Traditional Methods of Survey Validation" in this v15 n2 2017 issue of "Journal Measurement: Interdisciplinary Research and Perspectives," Andrew Maul writes that it is commonly believed that self-report, survey-based instruments can be used to measure a wide range of psychological attributes,…

Interest in Bayesian analysis of item response theory (IRT) models has grown tremendously due to the appeal of the paradigm among psychometricians, advantages of these methods when analyzing complex models, and availability of general-purpose software. Possible models include models which reflect multidimensionality due to designed test structure,…

The main challenge of ability tests relates to the difficulty of items, whereas speed tests demand that test takers complete very easy items quickly. This article proposes a conceptual framework to represent how performance depends on both between-person differences in speed and ability and the speed-ability compromise within persons. Related…

The challenge for a discussant of the Humphry article in this issue is that the profundity of the simple insights of the article, and the lucid arguments by which the insights are sustained, might be easily overlooked, undervalued, or misconstrued. At the risk of repeating major inferences already presented, one may note that the article…

Humphry's article, "The Role of the Unit in Physics and Psychometrics," offers fundamental clarifications of measurement concepts that Fisher hopes will find a wide audience. In particular, parameterizing discrimination while preserving statistical sufficiency will indeed provide greater flexibility in accounting "for the effects of empirical…

This commentary examines the role of the unit from the perspective of the definition of measurement in physics as the ratio of two magnitudes, one of which is defined as the unit; it is an important and timely contribution to measurement in the social sciences. There are many different points that could be commented upon, but the author will…

Compared to traditional test theory, where person measures are typically referenced to the distribution of a population, item response theory allows for a much more meaningful interpretation of measures as they can be directly compared to item locations. However, Stephen Humphry shows that the crucial role of the unit of measurement has been…

Humphry (this issue) deserves credit for drawing attention to the long-neglected fact that differences in item discrimination parameters are often due to empirical factors and not the product of random error components. In doing so, Humphry offers a psychometrically elegant, coherent, and practically important new model that is more flexible while…

The paper by Drs. Rupp and Templin provides a much needed step toward the general application of diagnostic classification modeling (DCMs). The authors have provided a summary of many of the concepts that one must consider to properly apply a DCM (which ranges from model selection and estimation, to assessing the appropriateness of the model using…