Final answer:
The method of interest arbitration in which an arbitrator must choose either the employer's or union's final proposal in its entirety is called Final-offer Total Package (FOTP).
Step-by-step explanation:
The form of interest arbitration that restricts an arbitrator's ability by requiring them to select either the employer's or union's final proposal on all matters in a dispute is known as Final-offer Total Package (FOTP). This approach is distinguished from others, such as issue-by-issue arbitration or split-the-difference rulings, by its all-or-nothing nature. The arbitrator must choose between the complete sets of terms presented by each side rather than being able to suggest a compromise or pick and choose between issues. FOTP can be seen as a way to encourage both parties to present their most reasonable offers in the hope that theirs will be chosen as the final terms of the agreement.