The main objective of a job analysis is to figure out the core  requirements that is involved with a specific position.  In essence, job analysis looks for 4 factors: Knowledge, Skill, Ability and Other characteristics.

K - knowledge refers to the familiarity with the job function
Ex. A good swim teacher would someone who knows how to swim
S - skill involves the skills that would be beneficial for the position
Ex. Someone with great communication skills can make a dependable sales person.
A - ability involves the ability to successfully execute the position
Ex.  A suitable secretary is someone who can type 120 words per minute.
O - Other characteristics would include the additional factors that would be beneficial for the position.
Ex. Creative thinking makes a good problem solver.

KNOWLEDGE . SKILL . ABILITY . OTHER 

Once you have analyzed the KSAO of the job position, you are ready to post job ads that will attract suitable applicants.  Four letters that simplify the hunt for the perfect candidate.