Final answer:
The National Labor Relations Board (NLRB) is the federal agency that interprets and administers the National Labor Relations Act, arbitrating disputes and ensuring fair labor practices.
Step-by-step explanation:
The federal agency designated to be the primary interpreter and administrator of the National Labor Relations Act is the National Labor Relations Board (NLRB). The NLRB was established to arbitrate between industry and labor in contract disputes and is responsible for deciding disputes related to establishing unions. It plays a vital role in protecting the rights of workers and promoting fair labor practices. The NLRB is responsible for arbitrating disputes between industry and labor, especially concerning contract disputes. It was set up to enforce procedures for establishing unions that firms must follow and serves as a key institution for protecting the rights of workers and facilitating fair labor practices.