RESEARCH
28
Six Sigma approach is to the traditional approaches work process and identify
find out the root causes of for achieving a high level of the root causes of defects
the problem, symbolically process quality
that deteriorate the work
represented by
Prior to the six sigma principle performance.
Y = f (x1, x2, x3......xn)
deployment, a performance To compare the quality
Y is an output represents the measurement system should level of the work process
problem or the symptom be developed. The key associated with CTQ, a six
occurring due to cause (s) X. activities of the performance sigma principle metric should
the input (s)
measurement system are be clarified. Of the several
While
the
outputs
are setting up a companywide available six sigma principle
important, Six Sigma focuses quality
control
strategy metrics, process capability
on controlling the inputs and policies and arranging index (CP) was adopted to
to get an output that has performance
indicators provide upper and lower
minimal variation and meets based on that strategy.
boundaries based on the
the customer specifications.
Inordertosetupperformance company's quality control
There may be a few to several indicators, it is necessary to strategy and policies
thousandinputs.itisimportant identify activities and key Sigma
level
could
be
to identify and prioritize factors that
(USL-MEAN )
them through subjective are critical
CP (Process Capability Index) = (3×STDEV)
and statistical analysis for to
the
improvement opportunities. success of
(Sigma Level) =3×Cp
Then, a relentless drive to the project in each phase. obtained by CP where the
improve and sustain the Toward this end, critical total quantitative data for the CTQ
improvements this is the main quality (CTQ) is the most evaluation can be collected
challenge of six sigma team closely related element to continuously without any
Not every process will end a
process
performance serious bias. If only the
up at 3.4 DPMO (6 sigma) indicator.
upper bound is given for the
and it may not be necessary For instance, if "productivity" purpose of controlling the
or it also may not be good is a performance indicator defect rate of CTQ, we can
enough,
depending
on for a certain project, the calculate the CP by setting
industry and critical nature reliability of the resource up a goal for the allowable
of process. For instance, the flow can be assumed to be performance level so-called,
3.4 DPMO rate is considered a main CTQ because it has upper specification level and
an inappropriate goal for the closest association with then by using the mean and
construction operations.
productivity.
standard deviation from the
However, the fundamental by defining and measuring collected data.
conceptoftakingthesixsigma the status of various CTQs Based on the estimated CP,
principle's statistical definition such as variations in cycle we can evaluate the sigma
associated with minimizing time, idle, or waiting time of level of the current CTQ of a
the defect rates along with labor/equipment, excess or specified work process
different sigma levels and shortage of inventory and USL=upper specification limit,
the continuous pursuit of percent of earned value MEAN=mean of the data;
performance improvement achieved, we can evaluate STDEV=Standard deviation of
can be a drastic extension of the level of sigma in the the data.

---