Interviewing is a two-way process in which both you and your prospective employer gather information. It helps both of you see if your skills and styles will mesh well. But, more than anything else, an interview determines whether you are well suited for the requirements of the position in the eyes of the employer.
Interviewers use a variety of techniques to help evaluate a candidate.
Your work will be evaluated and factored into the selection process. Formal questions are asked in the same manner for each applicant. Usually assessed with a rating sheet. Interviews for government positions are typically highly structured. Most difficult to prepare for as questions are unpredictable.