Evidence-centered assessment design (ECD) provides language, concepts, and knowledge representations
for designing and delivering educational assessments, all organized around the evidentiary argument an
assessment is meant to embody. This article describes ECD in terms of layers for analyzing domains, laying
out arguments, creating schemas for operational elements such as tasks and measurement models,
implementing the assessment, and carrying out the operational processes. It is argued that this framework
helps designers take advantage of developments from measurement, technology, cognitive psychology,
and learning in the domains. Examples of ECD tools and applications are drawn from the Principled
Assessment Designs for Inquiry (PADI) Project. Attention is given to implications for large-scale tests such as
state accountability measures, with a special eye for computer-based simulation tasks.