Observation (also called Job Shadowing) is a tool and technique of the PMBOK’s Collect Requirements process. The Collect Requirements process defines and documents the needs of the stakeholders as they relate to meeting the project objectives. This method consists of watching people perform their work. It can be useful in understanding how the work is actually done (which may be different than how it should be done, or how a manual states that it should be done, or how managers think it is being done). Also, some work processes may not be written anywhere and only the workers themselves may know how the work is actually done. At times, people are unable to clearly communicate how work is performed, so observing them is the best method. 

There are two approaches to observation: Passive (invisible) and Active (visible). In Passive observation, the observer does not interfere by asking questions or participating in the work—they simply observe and take notes (afterwards they may ask questions). In Active observation, the observer is free to ask questions and may even perform some of the work. In some cases, the observer may act as an apprentice. There are advantages to both methods. Passive observation provides a more accurate representation of how the work is performed because the observer interferes less. However, Active observation allows the observer to have a better understanding of the work by asking questions while the work is being performed and perhaps even gaining first-hand experience of performing the work.