Hyesun You, Minju Hong
Interdisciplinary understanding is critical for reasoning about complex socio-environmental phenomena, yet validated assessments of interdisciplinary learning remain limited. This study reports the development and validation of the Interdisciplinary Science Assessment of Carbon Cycling II (ISACC II), designed to measure college students’ integration of concepts across multiple scientific disciplines. Guided by a construct-modelling framework, we articulated a construct map, designed assessment items, and developed analytic scoring rubrics for constructed-response tasks. The final instrument includes 14 multiple-choice items and 10 constructed-response items. Data were collected from 556 students at two U.S. public research universities. Psychometric analyses combined confirmatory factor analysis and multidimensional item response theory. A two-factor model distinguishing disciplinary and interdisciplinary understanding demonstrated excellent fit (e.g. RMSEA ≈ .02, CFI ≈ .99). Item-level analyses indicated appropriate levels of difficulty and discrimination. Reliability was strong for the full assessment (α = .86; ω = .89) and the interdisciplinary subscale (α = .79; ω = .84). Inter-rater reliability for constructed responses was high (overall ICC [2,k] = .93; item-level ICCs = .84 – .99). Differential item functioning analyses across gender and ethnicity revealed no significant bias. The ISACC II offers a vetted tool for assessing and advancing interdisciplinary science learning related to global challenges.