(1) "Health care activity" includes any hospital, nursing home, institution, agency or establishment, exclusive of those operated by the state, its municipalities, or political subdivisions, having for one of its principal purposes the preservation of health or the care of sick, aged or infirm persons.(2) "Bargaining unit" includes any group of employees of a health care activity having substantially common interests with respect to working conditions. The composition of a bargaining unit may be determined by common consent between an employer and its employees, or, in the event either party shall apply to the director of labor and industries for a determination of the composition of a bargaining unit, it shall be determined by the director of labor and industries or his delegated representative. No bargaining unit shall be found appropriate if it includes guards together with other employees.(3) "Employee" includes any registered nurse or licensed practical nurse or service personnel performing services for wages for a health care activity. The term shall not apply to a member of a religious order assigned to a health care activity by the order as a part of his obligations to it; nor shall it apply to persons performing services in connection with healing by prayer or spiritual means alone in accordance with the tenets and practices of recognized church or religious denominations by adherents thereof; nor shall it apply to supervisors.(4) "Employer" includes any person, agency, corporation, company or other organization engaged in the operation of a health care activity, whether for profitable or charitable purposes.(5) "Supervisor" means any individual having authority, in the interest of the employer, to hire, transfer, suspend, lay off, recall, promote, discharge, assign, reward, or discipline other employees, or responsibly to direct them, or to adjust their grievances, or effectively to recommend such action, if in connection with the foregoing the exercise of such authority is not of a merely routine or clerical nature, but requires the use of independent judgment. Supervisor includes registered nurses only if administrative supervision is his or her primary duty and activity.(6) "Guard" means any individual employed as a guard to enforce against employees and other persons rules to protect property of the employer or to protect the safety of persons on the employer's premises.(7) "Director" means the director of the department of labor and industries.(8) "Department" means the department of labor and industries.