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Basic Concepts of Item Response Theory: A Nonmathematical Introduction IRT IRC

Livingston, Samuel A.
Publication Year:
Report Number:
ETS Research Memorandum
Document Type:
Page Count:
Subject/Key Words:
Item Response Theory (IRT), Calibration, Large-Scale Testing, One-Parameter Logistic Model, Two-Parameter Logistic Model, Three Parameter Logistic Model, Number Right Scoring, Rasch Model, Item Response Curve (IRC), Scaled Scores


This booklet is a conceptual introduction to item response theory (IRT), which many large-scale testing programs use for constructing and scoring their tests. Although IRT is essentially mathematical, the approach here is nonmathematical, in order to serve as an introduction on the topic for people who want to understand why IRT is used and what it does but are uncomfortable with the mathematics. The focus is on the basic types of IRT that are commonly used today.

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