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Standard Error of an Equating by Item Response Theory IRT

Author(s):
Lord, Frederic M.
Publication Year:
1981
Report Number:
RR-81-49
Source:
ETS Research Report
Document Type:
Report
Page Count:
9
Subject/Key Words:
Equated Scores, Error of Measurement, Item Response Theory (IRT), Mathematical Formulas, Test Theory

Abstract

A formula is derived for the asymptotic standard error of a true-score equating by item response theory (IRT). The equating method is applicable when the two tests to be equated are administered to different groups along with an "Anchor Test". Numerical standard errors are shown for an actual equating: 1) comparing the standard errors of IRT, Linear, and Equipercentile Methods; 2)illustrating the effect of the length of the anchor test on the standard error of the equating. (Author/BW). (25pp.)

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