That comes from the experience and intuition of managers. Just remember, the Rice profs said, that at first managers are going to be hard-pressed to come up with hard data to support a workable hypotheses. Then comes the work of mining for data to see if that manager's gut feeling was right or wrong. To test it, companies look first to their own books for information on customer revenues, defection rates, sales-call frequencies, and other costs of providing the service or product to individuals or groups of customers. With that information in hand, they talk to customers about customer satisfaction and perceptions.
Some companies do that themselves.
Others hire specialized firms to do surveys. With data in hand, changes are made. Unfortunately, that's not the end of the process. Profitable companies keep looking to make sure they are still meeting the needs of the customer.