Page 189 - Lean six sigma demystified

168 Lean Six Sigma DemystifieD

Critical to Quality (CTQ) Measures

There are only two types of defect-related problems: not enough of a good
thing or too much of a bad thing, either of which should be measurable and
easily depicted with a control chart. Since an increase in the “good” is often a
result of decreasing the “bad,” measures of the unwanted symptom make the
best starting place for improvement.
Since reducing the unwanted results of a process is often the best place
to begin, the area of improvement can usually be stated as reduce defects,
mistakes, errors, rework, scrap, or cost in a product or service. These are
often two sides of the same coin:

An Increase in . . . Is Equal to a Decrease in . . .

Quality Number defective
Percent defective
DPMO—defects per million opportunities
Profitability Cost of waste, scrap, and rework

Solving problems is usually easiest when you focus on decreasing the “bad” rather
than increasing the “good.” What are some of the current problems in your work
area? Are these problems due to delay, defects, or cost? Some examples include

• Complaints are defects.

• Outages or missed commitments are both defects and time problems.
• Waste of media, floor space, computers, networks, or people are cost problems.
• Rework to fix problems.

How could these be measured and depicted in a control chart to form the
basis of an improvement story?
? still struggling

Every process is error-prone. What kind of mistakes, errors or defects plagues your
process? what work products have to be reworked on a frequent basis? Count the
number of times things have to be reworked. How often do you have to scrap a work
product—printed document, out-of-spec part, or other interim product? These are
the defects, mistakes, and errors you can track, over time, to show performance.