extended · article · 2025

Construct comparability and the limits of post hoc modeling: insights from International Baccalaureate multi-language assessments

Louise Badham; Michelle Meadows; Jo‐Anne Baird; David Andrich

Construct comparability was investigated across different subjects in the International Baccalaureate (IB) Diploma Programme (DP). A Rasch Partial Credit Model (PCM) was applied to historical assessment data to generate statistical measures of the relative “difficulty” of IB subjects and languages. Specifically, analysis centered on different language versions of literature assessments, where exams differ in content, but are designed to assess the same target constructs. Rasch analyses were conducted sequentially in three subsets of data. Three different conceptualizations of the linking construct were compared, with the aim of narrowing the definition to increase the validity of the comparisons. These ranged from different DP subjects being linked by “general academic ability,” to linking English, Spanish and Chinese language versions of literature with the more relevant construct of “l...