Growing interest in interdisciplinary (ID) understanding has led to the recent development of four ID assessments, none of which have previously been comprehensively validated. Sources of evidence for the validity of tests include construct validity, such as the internal structure of the test. ID tests may (and should) test both disciplinary (D) and ID understanding, and the internal structure can be examined to determine whether the theoretical relationship among D and ID knowledge is supported by empirical evidence. In this paper, we present an analysis of internal structure of ISACC, an ID assessment of carbon cycling, selected because the developers included both disciplinary and ID items and posited a relationship among these two types of knowledge. Responses from 454 high school and college students were analyzed using confirmatory factor analyses (CFA) with the Mplus software for internal structure focusing on dimensionality, as well as functioning by gender and race/ethnicity, and reliability. CFA confirmed that the underlying structure of the ISACC best matches a two-factor path model, supporting the developers’ theoretical hypothesis of the impact of disciplinary understanding on interdisciplinary understanding. No gender effect was found in the factor structure of the ISACC, indicating that females and males have similar performance. Race/ethnicity performance was similar to other science assessments, revealing possible ethnicity bias on the part of the instrument. The reliability coefficients for the two-factor path model were found to be sufficient. This study highlights the importance of the internal structure of test instruments as a source of validity evidence and models a procedure to assess internal structure.

对跨学科 (ID) 理解的兴趣日益浓厚，导致最近开发了四项 ID 评估，这些评估以前都没有得到全面验证。测试有效性的证据来源包括结构效度，例如测试的内部结构。ID 测试可以（并且应该）测试学科（D）和 ID 理解，并且可以检查内部结构以确定 D 和 ID 知识之间的理论关系是否有经验证据支持。在本文中，我们对 ISACC 的内部结构进行了分析，这是一种碳循环的 ID 评估，之所以被选中，是因为开发人员同时包含了学科和 ID 项目，并假设了这两种知识之间的关系。使用 Mplus 软件对 454 名高中和大学生的反应进行了验证性因素分析 (CFA)，以分析内部结构的维度，以及性别和种族/民族的功能以及可靠性。CFA 证实 ISACC 的底层结构最符合双因素路径模型，支持开发人员关于学科理解对跨学科理解影响的理论假设。ISACC的因子结构中没有发现性别效应，表明女性和男性的表现相似。种族/民族表现与其他科学评估相似，揭示了仪器方面可能存在的种族偏见。发现双因素路径模型的可靠性系数是足够的。