Maintaining invariant scales in state, national and international level assessments.

大规模评估涉及国家之间、国家内部以及这些国家内部随时间的比较。由于许多原因，不可能对每个学生都提供相同的项目。 然而，这些项目必须在各组之间保持不变。 Rasch模型具有不变性作为内在属性，在检查这种不变性方面非常强大。该项目将首席调查员的基础研究带到行业合作伙伴中，以研究，应用和记录违反Rasch模型和不同数据收集格式的方式反映为规模变化，以及如何在统计和经验上控制这些变化。

Large scale assessments involve comparisons between countries, states within a country, and within these over time. For many reasons, identical items cannot be administered to every student. Nevertheless, the items must operate invariantly across groups. The Rasch models, which have invariance as an intrinsic property, are powerful in checking for such invariance. This project brings the basic research of the Chief Investigators to the industry partners to study, apply and document ways in which violations of Rasch models and different data collection formats are reflected as changes of scale, and how these might be controlled both statistically and empirically.