Useful for immediate feedback, for developmental purposes and for estimating performance -providing a simple, structured system is used. The presence of the observer can change the performance so the method should be handled sensitively. Impressionistic observation can be useful if supported by constructive feedback. Can be used by a group of peers to provide feedback as well as assessment. Intensive, lengthy training is required for high reliability if detailed checklists are used. Reliability, validity and manageability are fairly high when structured observation is used.