Final answer:
In a full-service agency, the research department is responsible for gathering, analyzing, and interpreting information that assists in the development of advertising strategies.
Step-by-step explanation:
In a full-service agency, the function of gathering, analyzing, and interpreting information that is useful in developing advertising is the responsibility of the research department. This department is essential because it helps to ensure that the advertising strategies are based on solid data and genuine understanding of the market, competitors, and consumers. The research department's role involves various activities such as conducting market research, analyzing consumer behavior, testing ad effectiveness, and staying abreast of industry trends to inform the advertising process. While other departments within an agency, such as the public relations office, marketing office, literary department, box office manager, house manager, and ushers, may contribute to the overall efforts of an agency, the research department is specifically tasked with the responsibility described in the question.