Page 251 - Design for Six Sigma a Roadmap for Product Development

Quality Function Deployment (QFD) 221

desirability index. This product, when summed over all the customer
features in the WHATs array, provides a measure of the relative impor-
tance of each CTS to the DFSS team and is used as a planning index
to allocate resources and efforts, comparing the strength, importance,
and interactions of these various relationships. This importance rating
is called the technical importance rating.

7.4.4 Importance ratings
Importance ratings are a relative measure indicating the importance
of each WHAT or HOW to the design. In QFD, there are two impor-
tance ratings:
■ Customer desirability index. This is obtained from the voice of the
customer activities such as surveys and clinics, and is usually rated on
the scale from 1 (not important) to 5 (extremely important) as follows:

Importance
Extremely Important 5.0
Very Important 4.0
Somewhat Important 3.0
A Little Import 2.0
Not Important 1.0

■ Technical importance ratings. These are calculated as follows:

1. By convention, each symbol in the relationship matrix receives a
value representing the strength in the (WHAT,HOW) cell.
2. These values are then multiplied by the customer desirability
index, resulting in a numerical value for symbol in the matrix.
3. The technical importance rating for each HOW can then be found
by adding together the values of all the relationship symbols in
each column.
The technical importance ratings have no physical interpretation, and
their value lies in their ranking relative to one another. They are utilized
to determine what HOWs are priority and should receive the most
resource allocation. In doing so, the DFSS team should use the technical
importance rating as a campus coupled with other factors such as dif-
ficulty, innovation, cost, reliability, and timing and all other measures
in their project charter.

7.4.5 Planning matrix
This task includes comparisons of competitive performance and identi-
fication of a benchmark in the context of ability to meet specific customer
needs. It is also used as a tool to set goals for improvement using a ratio