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.
Direct Observation allows the job analyst to see (and in some cases experience) the work environment, tools and equipment used, interrelationships with other workers, and complexity of the job.
Direct Observation of incumbents may be necessary to support testimony if the incumbent or applicant for the job has sued the employer. A Job Analysis is necessary to support personnel actions that were taken. However, the job analysis may be of limited value if the job analyst has not seen the incumbent perform the job. In other words, relying solely on the incumbent's description of their job may not withstand scrutiny in a court of law.
Testimony about jobs personally done is direct testimony and not subject to hearsay rules.
One problem with the direct Observation method of Job Analysis is that the presence of an observer may affect the incumbent causing the incumbent to alter their normal work behavior. It is important for the analyst to be unobtrusive in their observations. Incumbents may alter their work behavior if they know they are being observed.
This method is not appropriate for jobs that involve significant amounts of time spent in concentration or mental effort.