The fallacy of zero defects

Posted on October 21, 2011 by

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I recently had the zero defects phrase thrown at me, “we strive for zero defects in company X”, said the person (who appeared to have a serious crackberry habit). Hmm, I thought do you really know what you’ve just said to me? Is it possible to attain a zero defect level in a given process? It certainly sounds a reasonable concept and it may even motivate some people to attempt to attain this goal in the early days, weeks and months of a TQM program. However, as always not everything is exactly what is seems.

Whilst I respect Phil Crosby, who advocated many initiatives in addition to zero defects in his books (Quality Is Free: The Art of Making Quality Certain, Quality Without Tears: The Art of Hassle-Free Management, and Lets Talk Quality), he has some powerful detractors:

For example in the book Re-imagine—Business Excellence in a Disruptive Age, Tom Peters says:

“Zero defects is great … in a known environment. But it is Death itself … in Ambiguous Surroundings. So join me. Raise the Flag. 100% Against Zero Defects.”

Likewise, point 16 of Demings “deadly diseases and obstacles to success” (from Out of the Crisis) states:

“The fallacy of zero defects. Every system produces defects. Ultra high quality requires enormous sample universes to establish the defect rate.”

Also D.C. Montgomery, author of the book Introduction to Statistical Quality Control, agrees, commenting that these programs typically do not drive the “use of proper statistical and engineering tools into the right places of the organization,” and they “devote far too little attention to variability reduction.”

The focus on attempting to attain zero defects slows down continuous improvement because it requires massive effort on defect detection as opposed to prevention.

I would suggest that using DFSS for a product or service ensures that a low defect level from launch will effectively mean that once released from the design stage customer expectations and needs (CTQs) are completely understood and a virtually zero level of defects can be realised.

In any case, six sigma is about continually looking for ways to improve performance and learning from your mistakes. It has room for making some errors or producing some bad product. Specifically, it allows you to have three defects for every million opportunities – to me that is a virtually zero-defect performance. Indeed professionals in other areas also understand the fallacy of zero defects as well.

Do you strive for zero defects? How successful have you been? Leave a comment below.

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Posted in: Quality, Six Sigma