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Cognitive diagnosis using item response models

In this paper, I will describe a particular approach to cognitive diagnosis that is centered on the idea of developmental assessment, and illustrate how data from this approach can be modeled using explanatory item response models. The developmental assessment approach starts with the idea of a progression of learning embodied in what are called progress variables. In a progress variable, student understanding is conceptualized as a continuum with successive levels of development. Effectively, these are seen as a series of student conceptions – this is the first layer of diagnosis. Then, student misconceptions are seen as particular diagnoses within the student conceptions, forming a second layer of diagnosis. Explanatory measurement is introduced as a way to formally model the psychometrics of this situation, using the Berkeley Evaluation and Assessment Research (BEAR) assessment system as a specific example. The discussion is illustrated with examples from student learning about selected topics in scien...