The general purpose of job analysis is to document the requirements of a job and the work performed. Job and task analysis is performed as a preliminary to successive actions, including to define a job domain, write a job description, create performance appraisals, selection and promotion, training needs assessment, compensation, and organizational analysis/planning.

In the fields of Human Resources (HR) and Industrial Psychology, job analysis is often used to gather information for use in personnel selection, training, classification, and/or compensation.

Professionals developing certification exams use job analysis (often called something slightly different, such as "task analysis") to determine the elements of the domain which must be sampled in order to create a content valid exam. When a job analysis is conducted for the purpose of valuing the job (i.e., determining the appropriate compensation for incumbents) this is called "job evaluation."

There are several ways to conduct a job analysis, including: interviews with incumbents and supervisors, questionnaires (structured, open-ended, or both), observation, and gathering background information such as duty statements or classification specifications. In job analysis conducted by HR professionals, it is common to use more than one of these methods.

For example, the job analysts may tour the job site and observe workers performing their jobs. During the tour the analyst may collect materials that directly or indirectly indicate required skills (duty statements, instructions, safety manuals, quality charts, etc).

The analyst may then meet with a group of workers or incumbents. And finally, a survey may be administered. In these cases, job analysts typically are industrial psychologists or have been trained by, and are acting under the supervision of, an industrial psychologist.

In the context of vocational rehabilitation, the primary method is direct observation and may even include video recordings of incumbents involved in the work.

It is common for such job analysts to use scales and other apparatus to collect precise measures of the amount of strength or force required for various tasks. Accurate, factual evidence of the degree of strength required for job performance is needed to justify that a disabled worker is legitimately qualified for disability status.

In the United States, billions of dollars are paid to disabled workers by private insurers and the federal government (primarily through the Social Security Administration). Disability determination is, therefore, often a fairly "high-stakes" decision. Job analysts in these contexts typically come from a health occupation such as occupational or physical therapy.

Questionnaires are the most common methodology employed by certification test developers, although the content of the questionnaires (often lists of tasks that might be performed) are gathered through interviews or focus groups. Job analysts typically operate under the supervision of a psychometrician. Best for every company.