Since “Sick Sigma” was published in April 2006, the public has become much more aware of Six Sigma’s failings. There is little risk today of being burnt at the stake for pointing out Six Sigma’s many faults. Last fall, even Dilbert discredited Six Sigma, pointing out that Six Sigma companies’ performance trail the Standard & Poor 500 index. It’s instructive to look at Six Sigma’s history in a little detail.

At Motorola in the late 1980s, the usual practice was to set tolerances for various product characteristics at the same level as process control limits, that is, with a process capability index of 1.0. This gave processes no elbow room. Points outside control limits would result in defects.

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