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…

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 last 50 years of human and social science measurement theory and practice have witnessed a steady retreat from physical science as the canonical model. Humphry unapologetically draws on metrology and physical science analogies to reformulate the relationship between discrimination and the unit. This brief note focuses on why this reformulation…

The article by Stephen Humphry (this issue) is a technical tour de force. At one level, the author marvels at the ingenuity and sophisticated logic and argument on display. This is impressive work and thinking whichever way one looks at it. However, after twice re-reading the manuscript, the same question arises on the author's mind: What exactly…

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." A recent…

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…

In his opening statements, Humphry takes a critical attitude with respect to psychometric modeling. As he advances and discusses Michell's well-known criticisms, the reader is certain that this paper must have something on offer that deviates considerably from conventional psychometrics. After all "most psychometricians have either explicitly or…

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 for a…

Black, Wilson, and Yao (this issue) lay out a comprehensive vision for the way that learning progressions (or other "road maps") might be used to inform and coordinate formative and summative purposes of assessment. As Black, Wilson, and others have been arguing for over a decade, the effective use of formative assessment has great potential to…

The focus article "Road Maps for Learning: A Guide to the Navigation of Learning Progressions" by Black, Wilson, and Yao (this issue) is a veritable tour-de-force, covering a great deal of education ground while spanning the heights from models of the interplay among curriculum, pedagogy, and assessment to interpretations of student responses to…

The notion of the road map, advocated by Black, Wilson, and Yao (2011), and the associated minutiae of the construct map have several powerful features. At one level these notions assist the teacher to select and embody a suitable sequence of constructs within a specified curriculum. Whatever disparate sequenced pathways individual learners may…

Black, Wilson, and Yao (this issue) make a compelling case for a coherent model of curriculum, pedagogy, and assessment, all built around a well-specified theory of learning. Arguing that dominant assessment policies and practices tend to drive pedagogy and student attitudes toward learning in pernicious ways, Black et al. make an argument that is…

The Black, Wilson, and Yao (this issue) provide a wide-ranging commentary and vision of the interrelationships among curriculum, pedagogy, and assessment. Specifically, they describe how the Berkeley Evaluation & Assessment Research (BEAR) Center Assessment System can be used to integrate and systematize these areas. This commentary focuses on…