Worker-oriented procedures aim to examine the human attributes needed to perform the job successfully. These human attributes have been commonly classified into four categories: "knowledge", "skills", "abilities", and "other characteristics" (KSAO). "Knowledge" is the information people need in order to perform the job. "Skills" are the proficiencies needed to perform each task. "Abilities" are the attributes that are relatively stable over time. "Other characteristics" are all other attributes, usually personality factors. The KSAOs required for a job are inferred from the most frequently-occurring, important tasks. In a worker-oriented job analysis, the skills are inferred from tasks and the skills are rated directly in terms of importance of frequency. This often results in data that immediately imply the important KSAOs. However, it can be hard for SMEs to rate skills directly.