An introduction to Rasch measurement for scale development and person assessment

This article: a) outlines some of the limitations of True Score Theory, b) discusses some advantages of Rasch measurement, and c) compares the results of Rasch and factor analytic techniques applied to a common data set. Using a mail survey, 206 female members of a national nursing association completed Ryckman's (1982) Perceived Physical Ability Scale. Exploratory factor analysis identified one factor with a Cronbach alpha of .78. Rasch fit statistics also identified one dimension with a person reliability of .76. Rasch methods were also used to investigate the rating scale functioning, additional construct validity issues, and person diagnosis. Discrepancies between the two estimates of internal consistency are discussed and differences in the utility of the two methodologies are reviewed.