The performance of each employee in the skilled service, professional service, and management service, including special appointments in each classification of each of those services, shall be evaluated in accordance with this subtitle. The appointing authority shall ensure that each of the unit’s employees who is subject to this subtitle has performance evaluations in accordance with this subtitle and procedures established by the Secretary. Each supervisor of an employee subject to this subtitle shall attend mandatory training by the Department on the methods and procedures required in the performance appraisal process. Factors in evaluating a manager’s or supervisor’s performance shall include: attendance at any required performance appraisal training; adherence to established methods and procedures in conducting performance appraisals; the timely completion of performance appraisals for employees assigned to the manager or supervisor; and subject to subsection (e) of this section, if required by the manager’s or supervisor’s supervisor, the results of an anonymous survey of employees assigned to the manager or supervisor in accordance with procedures established by the Secretary. An anonymous survey of the employees of a manager or supervisor may be performed only if more than five employees are assigned to the manager or supervisor.