This book examines the various areas of mathematics education and neighboring disciplines that have recently contributed to a better understanding of the still vague construct of diagnostic competence. The work addresses the nature, development and effect of diagnostic competence in mathematics instruction, with a focus on the professional development of teachers.

Part 1. The Nature of Diagnostic Competence - Conceptualizing and Measuring Facets of Diagnostic Competence.- 1. Diagnostic Competence of Mathematics Teachers - Unpacking a Complex Construct.- 2. Diagnostic Skills of Mathematics Teachers in the COACTIV Study.- 3. Competences of Mathematics Teachers in Diagnosing Teaching Situations and Offering Feedback to Students: Specificity, consistency and reification of Pedagogical and Mathematical Discourses.- 4. Diagnostic Competence for Dealing with Students' errors - Fostering Diagnostic Competence in Error Situations.- 5. Factors Influencing the Accuracy of Diagnostic Judgments.- 6. Diagnostic Competences of Mathematics Teachers with a View to Processes and Knowledge Resources.- 7. Revealing and Promoting Pre-Service Teachers' Diagnostic Strategies in Mathematical Interviews with First-Graders.-  Part 2. Developing Diagnostic Competence and Applying Diagnostic Competence in the Classroom - Models for Teacher Training.- 8. Developing Diagnostic Competence Through Professional Learning Communities.- 9. Supporting Mathematics Teacher Diagnostic Competence Through the use of one-to-one, Taskbased Assessment Interviews.- 10. Diagnosing Learning Goals: An Often Overlooked Teaching Competency.- 11. Improving Teachers' Assessment Literacy in Singapore Mathematics Classrooms: Authentic Assessment Task Design.- 12. Developing Prospective Teachers' Ability to Diagnose Evidence of Student Thinking: Replicating a Classroom Intervention.- 13. Specific Mathematics Assessments that Reveal Thinking: An Online Tool to Build Teachers' Diagnostic Competence and Support Teaching.