With direct Observation, the trained job analyst can obtain first-hand knowledge and information about the job being analyzed. Other Job Analysis methods (such as the interview or questionnaire) only allow the job analyst to indirectly obtain this information. Thus, with other methods of Job Analysis, sources of error (ommissions or exaggerations) are introduced either by the incumbent being interviewed or by items on the questionnaire. With direct observation of the incumbent, these sources of error are eliminated.