Six 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 Process Control.
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