Different criteria have been adopted for classifying customer requirements,
such as empirical observation, mode statistics, and customer satisfaction coefficient
(Berger et al., 1993). Timko (Berger et al., 1993) proposes a twodimensional
representation of Kano quality category based on the customer
satisfaction coefficients. In particular, a positive number is used to represent
the relative value of meeting the respective customer requirement, whilst a negative
number is used to reflect the relative cost of not meeting this customer
requirement. However, classification criteria are not explicitly defined in this
model. DuMouchel (Berger et al., 1993) proposes a graphical Kano diagram
that is based on predefined scales related to the customer’s satisfaction and
dissatisfaction. Each customer requirement can be represented as a pair of satisfaction
and dissatisfaction values. The nature of a customer requirement can
be delineated by the quadrant into which that point falls. However, it is very
subjective to classify the customer requirements into four quadrants because of
a lack of logical classification criteria.