Based on the above formulation, the FRs can be classified into four categories,
i.e., indifferent, must-be, attractive and one-dimensional, as shown
in Figure 3. A threshold value of the importance index, r0, is used to differentiate
important FRs from less important ones. If ri r0, fi is considered
as unimportant, and thus called an indifferent FR. The region
defined by the sector OFI in Figure 3, where the radius is smaller than
r0, is considered as the indifferent region. Hence r0 is called an indifference
threshold.
Likewise, a lower threshold value of the satisfaction index is defined as aL,
such that for fi, if ri > r0 and ai aL, it is considered as a must-be FR. The
region of the must-be FRs corresponds to the sector DEFG.
A higher threshold value of the satisfaction index is defined as aH, such that for
fi, if ri > r0 and ai > aH, it is considered as an attractive FR. The region of the
attractive FRs is shown as sector ABHI.
Table 3 Scores for functional/dysfunctional features
Answers to the Kano question Functional form of the question Dysfunctional form of the question
I like it that way (like) 1 0.5
It must be that way (must-be) 0.5 0.25
I am neutral (neutral) 0 0
I can live with it that way (live with) 0.25 0.5
I dislike it that way (dislike) 0.5 1
Table 4