It has been argued that the single most important difference between products and services is the characteristic of intangibility. In fact, it has been said that intangibility is the key to determining whether or not an offering is a service or product (Zeithaml and Bitner, 1996). This characteristic has a profound effect on the marketing of services (Lovelock, 1991; Rushton and Carson, 1989). Levitt (1981) argued that special difficulties arise from this intangibility which lead to quality control problems for the producer and evaluation problems for the consumer. It is this intangibility, or lack of physical attributes, that most likely is the reason for service variability, inseparability and perishability.
             Besides the concept of the lack of physical attributes of the offering (outcome), there is also the concept of physical evidence of the process which needs to be taken into consideration in an evaluation of intangibility. "Physical evidence is the environment in which the service is delivered and where the firm and the customer interact; and any tangible commodities that facilitate performance or communication of the service (Zeithaml and Bitner, 1996, p. 518)". The physical evidence of the service production process can be used to communicate service quality attributes and create the service experience. A distinction should be made between the degree of intangibility of the actual service and the intangibility, or lack of physical evidence, of the production process. It has been suggested that three types of inputs can be processed: the customer (dental services), materials (car wash), and information (education) (Morris and Johnston, 1987). Consumers evaluate services in regards to those elements that they actually experience in the course of the service delivery and - of course - on the perceived service outcome (Lovelock, 1991, p. 14). Recognizing this, a useful distinction might be made in services research between the pro...