skip to main content skip to footer

A Survey of Equating Methods Based on Item Characteristic Curve Theory

Lord, Frederic M.
Publication Year:
Report Number:
ETS Research Bulletin
Document Type:
Page Count:
Subject/Key Words:
College Board, National Science Foundation (NSF), Equated Scores, Item Response Theory, Mathematical Formulas, Models, Test Theory


A variety of equating methods based on icc theory are surveyed and compared with nonlinear conventional methods. In many cases, the icc model replaces a nonlinear equating problem by a linear one. This helps the stability of the equating near the extremes of the data. Strictly speaking, icc methods are the only methods appropriate when the tests to be equated are given (with an anchor test) to groups differing in ability. It seems likely that icc methods can reduce drift in equating chains involving many links. Research into the practical value of preequating is recommended. (37pp.)

Read More