Page 314 - Six Sigma Demystified

294 Six SigMa DemystifieD

for those four conditions of cycle time, personal response [(210, yes), (210,
no), (330, yes), (330, no)], and plot the average response on the interaction
plot.

Interpretation

In this interaction plot, there are two lines: The line for cycle time equals 210
is relatively flat, with little change in customer satisfaction as we move from
the personal response (no) to the personal response (yes) condition. The line
for cycle time equals 330 is relatively steep, with a big difference in customer
satisfaction between the personal response (yes) and the personal response
(no) conditions. Since the effect of cycle time on satisfaction varies depending
on whether there was a personalized response or not, we say that there is an
interaction between cycle time and personalized response. Interactions are eas-
ily spotted on an interaction plot by nonparallel lines, such as shown in the
figure.

lean methodology

Lean is a set of principles and methodologies for improving cycle times and
quality through elimination of waste, sometimes known by its Japanese name
of muda. Lean thinking allows us to distinguish between value-added and non-
value-added activities. The immediate result is the removal of unnecessary
non-value-added activities. The objective is to improve cycle times, reduce

waste, and increase value to the customer.
Lean thinking has been shown to reap dramatic benefits in organizations.
Organizations are able to sustain production levels with half the personnel,
improving quality and reducing cycle times from 50 percent to 90 percent
(Womack and Jones, 1996).
The lean methodology is credited to Taiichi Ohno of Toyota; it has been
popularized by James Womack and Daniel Jones in The Machine That Changed
the World and Lean Thinking. The methodology goes by several names, including
lean manufacturing, when used in manufacturing applications, and the Toyota
Production System, owing to its origins. The more recent label of lean thinking,
used by authors Womack and Jones, applies the methodology across a broad