Final answer:
D. Customer complaints should be processed promptly
The criterion that customer complaints should be processed promptly is most useful for evaluating a customer-service group's performance, as it shows efficiency and directly affects customer satisfaction.
Step-by-step explanation:
The most useful criterion to a sales department manager in evaluating the performance of the manager's customer-service group among the given options would be D. Customer complaints should be processed promptly.
Prompt processing of customer complaints shows the efficiency and responsiveness of the customer service team. Unlike merely answering inquiries within a week or maintaining a positive attitude, which are also important, promptly addressing complaints directly correlates with customer satisfaction and operational effectiveness.
Being professional and resourceful in handling customer complaints not only improves the perception of the customer service team but can also lead to increased job satisfaction among employees. As seen in the provided example, resolving customer complaints quickly through thoughtful actions—like introducing floor markings to streamline a confusing queue system—not only resolved the immediate issue but also resulted in no further complaints during high traffic periods. Thus, demonstrating that prompt solutions to problems effectively enhance customer service.
This criterion aligns with the principles of returning promptly from breaks, maintaining a professional appearance, and demonstrating support for the company's overall goals to provide excellent customer service. Furthermore, it ensures that the customer service clerks are focused and carry out tasks in a timely manner, which contributes to the overall productivity and customer satisfaction levels.