The PSEA gives managers with staffing authority broad discretion to establish necessary qualifications for the position they want to staff, as well as to choose and use assessment methods that will enable them to determine whether a person meets the essential qualifications. The methods must be reasonable, and assess the essential qualifications fairly - a simple error or omission is not considered an abuse of authority.  The onus would be on you to provide evidence that there was an abuse of authority in the appointment process.