Final answer:
The ethical principle that ensures equality of service by treating equals impartially is justice.
Step-by-step explanation:
The ethical principle that means that equals should be treated the same or impartially to provide equality of service is justice. Justice insists that the distribution and practice of healthcare should be fair and equitable. In clinical settings, patients should be treated similarly in relevant circumstances, and similar cases should be treated alike. Similarly, in clinical trials, all participants should be treated fairly and equally, without any special treatment given to certain individuals. The principle of justice promotes the impartial treatment of individuals and aims to ensure equality of service.