Scale Anchoring with the Rasch Model

Scale anchoring is a method to provide additional meaning to particular scores at different points along a score scale by identifying representative items associated with the particular scores. These items are then analyzed to write statements of what types of performance can be expected of a person with the particular scores to help test takers and other stakeholders better understand what it means to achieve the different scores. This article provides simple formulas that can be used to identify possible items to serve as scale anchors with the Rasch model. Specific attention is given to practical considerations and challenges that may be encountered when applying the formulas in different contexts. An illustrative example using data from a medical imaging certification program demonstrates how the formulas can be applied in practice.