We established the validity of the Symphony assessments in several ways. First, the problems were written in alignment with the Common Core State Standards. Thus, Symphony assessments addresses standards that students currently see on state tests, as well as topics that students will encounter in later years when CCSS computer-based state assessments are implemented. Second, we correlated the performance of students from New York and Illinois on the Symphony assessments with their scores on their respective state’s mathematics tests. In both cases, we found excellent correlations, thus validating the content and the scoring of the Symphony assessments. Finally, the construction of the Symphony assessments is supervised by professional psychometricians with extensive experience in commercial and state-level testing. In-depth research was performed into the quality of the test as a whole, as well as that of the individual questions. We recently reported some of the findings at the International Association for Computerized Adaptive Testing (IACAT).
The full study is available here: https://symphonylearning.com/documents/Assessment_ReliabilityValidity.pdf