The customer requirements categories and improvement ratio. High level of customer requirements (CR)
should be considered ‘‘purchase motives’’. Therefore, at this stage, we have first identified each customer’s
needs and the degree of importance of each need through interviews or Delphi methods. Then, by applying
the Kano model combined with Fuzzy mode, we are able to categorize each customer requirements based on our understanding of customer purchase motives. For example, if customer requirements were categorized
as ‘‘must-be’’, these requirements were considered extremely important by customers. Thus, the
designers should incorporate these requirements as top priorities during the system design. On the other
hand, if these requirements were categorized as ‘‘indifferent’’ or ‘‘reverse’’, then, to avoid any potential customer
discomfort with the system, the designers do not need to consider requirements which are deemed
‘‘indifferent’’ or ‘‘reverse’’ during the system design. Clearly, since the quality category of each CR varies,
the improvement ratio of the design system will be different.