Rasch Measurement Transactions, Part 1 and 2

Rasch Measurement

Transactions of the Rasch Measurement SIG American Educational Research Association

Objectivity is a cornerstone of all measurement. It requires that agent calibrations (e.g., item difficulties) be independent of the sample of objects (e.g., persons) used in the calibration procedure. Object measures must also be independent of the particular agents used to obtain them. Thurstone (1928) stated: “…the scale values of the statements of opinion must be as free as possible, and preferably entirely free, from the actual opinion of individuals or groups.” As Wright & Stone (1979) remark, Loevinger (1947) offered a similar formulation as a criterion for absolute scaling, but it was Rasch (1961) who made what he called “specific objectivity” the central requirement of a new approach to measurement.