Educational Testing Service (ETS) was founded with a dual mission: to provide high-quality testing programs that would enhance educational decisions and to improve the theory and practice of testing in education through research and development (Bennett 2005; Educational Testing Service 1992). Since its inception in 1947, ETS has consistently evaluated its testing programs to help ensure that they meet high standards of technical and operational quality, and where new theory and new methods

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... called for, ETS researchers made major contributions to the conceptual frameworks and methodology. This chapter reviews ETS's contributions to validity theory and practice at various levels of generality, including overarching frameworks (Messick 1988 (Messick , 1989 , more targeted models for issues such as fairness, and particular analytic methodologies (e.g., reliability, equating, differential item functioning). The emphasis will be on contributions to the theory of validity and, secondarily, on the practice of validation rather than on specific methodologies. Validity Theory General conceptions of validity grew out of basic concerns about the accuracy of score meanings and the appropriateness of score uses (Kelley 1927), and they have necessarily evolved over time as test score uses have expanded, as proposed interpretations have been extended and refined, and as the methodology of testing has become more sophisticated.