Evidence-Centered Design

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Authors: Louise Yarnall and Geneva Haertel
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Overview

Evidence-centered design, or ECD for short, takes the art of test design and turns it into a science. Test development usually involves assembling various items into a test and then using statistical techniques and expert review to check for technical quality. ECD reduces the trial-and-error process, and leads to better measures. ECD involves justifying many design decisions before the first test item is selected or developed. Through ECD process, test developers create a list of the types of evidence known to accurately reflect what someone knows and can do. Creating this list is particularly valuable when designing tests of hard-to-measure knowledge, skills, and psychological states. ECD is becoming a testing industry standard and provides the kind of documentation that is often imperative in legal situations when evidence of a test’s validity is required. This primer will provide a quick overview of this assessment design practice and both its benefits and costs.

To begin the ECD process, test developers study relevant learning sciences research, gather input from subject matter experts, and review previous tests, assessment tasks, scoring rubrics, and scales. Such initial groundwork is important because test designers rarely develop an accurate and reliable measure on their first try. All this upfront work is carefully documented so that later, after the test is administered, ECD test designers may refer back to this rich documentation to systematically review and revise items and tasks to increase comprehensibility, precision and reliability. Moreover, the ECD documentation means that the designers have evidence on which to base each subsequent revision to the test questions, media representations, or scoring rules. They also can reuse these documents to efficiently create tests of similar knowledge and skills.

While large-scale testing companies may engage professional item designers and measurement experts in using ECD, the basic ECD principles can serve as a useful guide to teachers and human resources professionals when selecting testing materials for use. These principles may also be helpful to parents and students when considering the fairness of tests administered in schools and elsewhere, especially when high stakes decisions are being made (e.g., admission to a university, a certification examination, for use as evidence of an instructor’s competency). This primer summarizes the three core concepts that must be considered when of designing assessments—Cognition, Observation, and Interpretation (presented in the assessment triangle below), and how they align with the ECD process to contribute to better test design and test product selection.


The Assessment Triangle.
(Pellegrino, Chudowsky, & Glaser, 2001, p. 44)

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