Measuring students' scientific content and inquiry reasoning

Recently, several important documents have promoted inquiry-based science as the main way for science to be taught and learned. In addition, there have been advancements made in the measurement sciences that allow for sophisticated and complex ways to score and interpret student responses on assessment tasks. However, while many studies have shown the benefits of scientific inquiry in the classroom and others have described new types of psychometric models available for scoring analysis, few have combined the two to develop a better understanding of how students "know" science. This paper briefly describes an assessment system used to create items that systematically measure both students' content knowledge as well as two complex inquiry-reasoning skills. Then, using student responses to an assessment made using this system we employ multidimensional psychometric models to allow us to explain the nature of the types of knowledge students draw on when encountering scientific scenarios.