These different standards and criteria of consumers and providers for evaluating quality of service need to be brought closer together. Usually, consumers purchase products and evaluate them through their experience of using them. If they decide to purchase the products again, because of their positive experience, they then tell others of the qualities of the products. So the image of the products may be established during the consumer's usage, evaluation and word-of-mouth advertising. On this reason, it is meaningless for providers to evaluate the products and make efforts to improve the products based only on their own standards and criteria without considering consumers’ standards and criteria.
In the service area, the quality is very superficial and subjective, and thus it is difficult to evaluate precisely or control the service. (Yoo, 1996)