Sigma uses a number of specialized
measures (metrics). The most fundamental
is the Defects Per Million Opportunities
(DOMO) measure. The aim of six sigma is
to achieve less than 3.4 DPMO. A process
that gives 3.4 DPMO has achieved 'six sigma'
The Rolled Throughput Yield (RTY) is a
key tool in achieving this. The individual
yields at each process step might look,
at first site, quite good, but the First
Pass Yield might be significantly lower.
Even when the First Pass Yield at each process
step looks satisfactory the overall or Rolled
throughput Yield may be low.
The sigma metric is an alternative to the
traditional process capability and process
performance measures used in Statistical
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