In "Using Learning Progressions to Design Vertical Scales that Support Coherent Inferences about Student Growth" (hereafter ULR), Briggs and Peck suggest that learning progressions could be used as the basis of vertical scales with naturally benchmarked descriptions of student proficiency. They propose and provide a single example of a…

The literature on bibliometric indices for assessing scholarly impact, in particular the "h" index (Hirsch, 2005) and its many variants, is extensive, but nevertheless Ruscio and colleagues (this issue) succeed in making a valuable contribution. They have made the effort of collecting publication and citation data for no less than 1,750…

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…

Ruscio and colleagues (Ruscio, Seaman, D'Oriano, Stremlo, & Mahalchik, this issue) have done a great service by systematically comparing indices of scholarly impact. Three aspects of their work are particularly valuable: (1) Their assessment of the proliferating collection of metrics, whose development has become something of a cottage industry,…

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…

In their article Ruscio et al. (Ruscio, Seaman, D'Oriano, Stremlo, & Mahalchik, this issue) present a comparative study of some of the different variants of the "h" index. The study evaluates a total of 22 metrics, including the "h" index and "h"-type indices, as well as other conventional measures. The novelty of their work is to a large extent…

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…

Humphry (this issue) has written a thought-provoking piece on the interpretation of item discrimination parameters as scale units in item response theory. One of the key features of his work is the description of an item response theory (IRT) model that he calls the logistic measurement function that combines aspects of two traditions in IRT that…

Behavioral scientists have struggled with units of measurement for as long as they have struggled with measurement itself. Psychology's sole attempt at an explicit unit of measurement--the Lexile Framework for Reading (Stenner, Burdick, Sanford, & Burdick, 2006)--has been and continues to be ignored by the psychometric "cognoscenti."…

The purpose of this article is to examine the role of the unit in physics in order to clarify the role of the unit in psychometrics. Based on this examination, metrological conventions are used to formulate the relationship between discrimination and the unit of a scale in item response theory. Seminal literature in two lines of item response…

This article presents Stephen Humphry's response to the commentaries for his article "The Role of the Unit in Physics and Psychometrics." The commentaries covered a range of important considerations and implications. Given that the author fully agrees with the majority of the content, attention will be confined mainly to points that call…

Describing, explaining, and discussing various modern indices of scholarly impact as accomplished by Ruscio, Seaman, D'Oriano, Stremlo, and Mahalchik (this issue) is highly commendable, as such measures get increasingly important in hiring and promotion decisions. The author agrees with almost all points made in the target article, except the…

Ruscio and colleagues (Ruscio, Seaman, D'Oriano, Stremlo, & Mahalchik, this issue) provide a thoughtful empirical analysis of 22 different measures of individual scholarly impact. The simplest metric is number of publications, which Simonton (1997) found to be a reasonable predictor of career trajectories. Although the assessment of the scholarly…

Ruscio et al. (Ruscio, Seaman, D'Oriano, Stremlo, & Mahalchik, this issue) write of a thing with which scientists and scholars are all too familiar, the assessment of published research and of its authors. The author was startled to discover how little the agenda of the paper seems to engage with factors one relies on for salary and promotion…

In this commentary, the author points out few issues, one being that there are models mislabeled as diagnostic, which deal with linear decompositions of item difficulties rather than estimating multidimensional skill variables. The author discusses the issue that there are many new names for essentially well-known models for multiple simultaneous…