Cognitive diagnostic models (CDMs) have received much interest within the field of language testing over the last decade due to their great potential to provide diagnostic feedback to all stakeholders and ultimately improve language teaching and learning. A large number of studies have demonstrated the application of CDMs on advanced large-scale…

As a high-stakes standardized test, IELTS is expected to have comparable forms of test papers so that test takers from different test administration on different dates receive comparable test scores. Therefore, this study examined the text difficulty and task characteristics of four parallel academic IELTS reading tests to reveal to what extent…