Quality assurance in assessment requires attention to validity, reliability and fairness. Assessment provides important information about students and educational processes that is then used for a variety of purposes. We need to ensure that appropriate, reasonable and fair conclusions and decisions about students’ learning are based on sound evidence. Validation involves investigating what it is that assessments are designed to find out and the extent to which this is realised in practice. Assessments also need to provide stable results so that teachers, students and others can have confidence in the information provided. Approaches to maximising and estimating reliability vary, with some focusing on the properties of the test itself (e.g. internal consistency) and others focusing on the consistency with which items are scored. All assessment results contain some error and there are appropriate ways to communicate such uncertainty to test users. One of the eight key principles emphasised in the book focuses on ethical and fair use of assessment, concepts that are linked to validity and reliability in Chapter 2.