How to design a useful test: the principles of assessment

Good assessment requires a variety of methods; no single method can test the whole of medical competence and performance. Designing assessment programmes and selecting the best instruments for each purpose is not easy. To complicate matters further, medical education is a rapidly evolving discipline. This may easily lead to a perception that assessment is not scientific because the truths of yesterday are obsolete and will be replaced with new ones. A step in setting up an assessment system is to choose the most appropriate methods. Several criteria that can be used in the evaluative process have been described in the literature. The popular ones include reliability, validity, and cost-effectiveness. Popular assessment instruments include written assessment instruments, objective structured clinical examinations, and simulated patient-based examinations. Unless one controls with advanced psychometric techniques, the variability in test difficulty is sizeable.