There is no law that states all candidates being interviewed for open requisitions must go through the same number of interviews. In fact, it is common for higher level positions (e.g. senior management) to have more steps in the hiring process and more interviews than, for example, entry-level positions. Best practices for hiring processes do, however, include being consistent with the steps each candidate for a specific requisition must go through. If a written test is given to one applicant for a particular requisition, then all applicants for the requisition should be given the same test. Also, when interviewing candidates for a particular requisition, it is a best practice to ask all applicants for that req. the same core questions. This allows the interviewers to compare answers to the same questions across the board for all candidates being considered.