Page 49 - Design for Six Sigma for Service (Six SIGMA Operational Methods)

Design for Six Sigma Road Map for Service 31

Then the most appropriate set of critical-to-satisfaction (CTS) metrics are
determined in order to measure and evaluate the design.
The detailed subtasks in this step include

• Identify methods of obtaining customer needs and wants.
• Obtain customer needs and wants and create a VOC list.
• Translate the items on the VOC list into functional and measurable
requirements.
• Finalize requirements.
• Identify CTSs as critical-to-quality, critical-to-delivery, critical-to-cost, etc.
DFSS tools used in this phase include

• Market and customer surveys
• Quality function deployment
• Kano analysis
Example 2.1: Customer Needs for Restaurant Service
This example (from Ramaswamy 1996) shows how VOC data can be used to
derive key CTS metrics in the restaurant business. The VOC data are often dis-
organized, nonspecific, and nonquantitative. Table 2.1 is the list of customer
needs for restaurant service.

An affinity diagram or the KJ method (Shigeru 1988) can be used to analyze
and organize the voices of customers into a CTS tree. A CTS tree is a refined
multilevel attribute that characterizes some critical characteristics for
customer satisfaction. An affinity diagram is a well-known method that was
developed in Japan, and it is a standard technique used in Six Sigma. By
using the affinity diagram, the following three-level preliminary CTS tree is
derived from the VOC data in Table 2.1 and is listed in Table 2.2.

Therefore, the first-level CTS factors are
Satisfying food
Clean and attractive surroundings
Good service
The second-level CTSs explain the first-level CTSs, and they are the
aggregated categories of original customer statements. For a complete set of
CTSs, we still need quantitative measures. For example, “short wait for table”
is one third-level CTS, but how short is short? 5 minutes? or 10 minutes?
Similarly, the CTS “food tastes good” does not indicate whether our food
tastes good enough now. Also, we need to know the relative importance of
each CTS item; for example, for the average customer which is more
important, the taste or the nutrition of the food? All this needed information
can be found by many means, such as by a specially designed customer survey,