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Bayesian Networks in Educational Assessment

Cognition and Assessment

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ACED Cognitive Model

ACED was designed using the evidence-centered assessment design (ECD) methodology. The means that the assessment design was organized into a collection of models called the Conceptual Assessment Framework?.

The Proficiency Model describes the variables representing knowledge, skills and abilities and their relationships. The ACED Proficiency Model describes skills related to arithmetic, geometric and other recursive sequences, concentrating on the various ways they can be represented (using examples, tables, pictures and formulae). Although the proficiency model was developed for all three branches, tasks were developed only for the geometric sequences.

The Task Models? describe templates for the development of the tasks. In ACED, these templates were augmented to include task specific feedback, informing the student about the correct solution path. The ACED Task Models? were produced both by reverse engineering existing geometric series items, and by producing model for automatic item generation. Note that ACED task were designed to be used with two kinds of feedback: task-specific elaborated feedback and accuracy only (correct or incorrect) feedback.

The Evidence Models? describe the relationship between the Proficiency Variables? and the Observable Outcome Variables? as well as how the observable variables are defined from work product of the task. In ACED all of the observables are binary variables (Correct or Incorrect) and hence the Evidence Model can be represented as a row in the Q-Matrix.

The Assembly Model? describes what collection of tasks constitutes a valid form of the assessment. Together the Assembly model and collection of Evidence Models determine the Q-Matrix of the assessment. The ACED Assembly Model had two options for task selection: Adaptive (using the Weight of Evidence? envelope) and Linear (using a fixed sequence).

As ACED was scored using StatShop?, which requires that the ECD models be specified using XML. An HTML translation of the complete model is available.


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ACED development and data collection was sponsored by National Science Foundation Grant No. 0313202.

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