Six Sigma or 6 Sigma
Level of process
performance equivalent to producing only 3.4 parts per million defects
or has a yield of 99.9997%. (Also see RTY,
(Rolled throughput yield)) Used to improve processes
using a sigma based process
measurement and/or striving for a six sigma level of performance. (See
below or our page on the original
six sigma theories and concepts) Used
in quality assurance to measure a
quality level. Also used by management in
various implementations to measure performance of services and the like.
Almost always related to a quality
improvement plan and not quality
assurance system. Can also be related to only cost improvement
strategies. Developed by Motorola in the 1980's.
Using the theory that approximately
2700 parts per million, (PPM), parts/steps will fall outside the
normal variation of +/- 3 Sigma.
In spite of this,
when we build a products containing 1200 parts/steps, we can expect 3.24
defects per unit (1200 x .0027), on average. The result of this is a rolled
yield of less than 4%. That is equivalent to fewer than 4 units out
of every 100 will go through the complete manufacturing process without
any kind of a defect.
Therefore, for a product to be built
"defect free", it must be designed
to tolerate characteristics or parameter,
which are significantly more than +/- 3 sigma away from the mean.
(also see our page DFSS,
design for six sigma)
It can be shown that a +/- 6 sigma can be
expected to have no more than 3.4 parts per million defective
for each characteristic, even if the process mean were to shift by as
much as +/- 1.5 sigma. In the same case as above, a product containing
1200 parts/steps, we can now expect only only 0.0041 defects per unit
(1200 x 0.0000034). This would mean that 996 units out of 1000 would go
through the entire manufacturing process without a defect as the
distribution below shows.
Both our software
products are geared to this end. And at only $150.00 and $65.00, (USD),
our software can get you going quickly.
