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Six Sigma

  • Six Sigma is a statistical approach which aims to drive up profits by putting special effort into ensuring goods or services conform to specification


  • It’s applicable to repetitive, relatively simple processes


  • Six Sigma is about eliminating unpleasant surprises and broken promises via:
    • Reducing any variation in the outputs from processes – defects or delivery times say – by ensuring virtually all meet certain minimum standards
    • Reducing waste and inefficiency
    • Redesigning a company’s products and internal processes so that customers get what they want, when they want and when they were promised


  • It’s not about averages but removing variation from customers’ interfaces with you


  • Getting things right 95% of the time is often just not good enough:
    • Deliveries to your home must be made when you’re in and waiting, not an hour or two later when you’ve had to go back to work
    • Personal computers must work when millions switch them on, every time, not 99 times out of 100
    • Airlines must not lose luggage, hospitals must not make mistakes – for you


  • Six Sigma is Statistical Process Control with extremely strict control limits:
    • SPC usually requires some 99.97% of the output from any process to fall within three standard deviations of the average – in other words 0.03% (3 defective items in every 10,000) may fall outside this range
    • Six Sigma aims for no more than 3.4 defects per million – covered by a range of 6 standard deviations from the average
    • The latter maximum failure rate is vital for a company like Intel – imagine if you bought a computer which often didn’t work because of a dodgy chip they’d made


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