It is surprising that a common topic of debate among quality professionals today is whether the “Zero Defects” concept is valid.

“Zero Defects” is a motivational management approach that first appeared in the “Quality and Reliability Assurance Handbook – A Guide to Zero Defects” (4155.12H) published by the U.S. Department of Defense on November 1, 1965, which explained:

Zero Defects is a motivational approach to the elimination of defects attributable to human error.

And:

Zero Defects is dedicated to preventing defects by detecting and removing the causes of their generation. This is an attempt to reverse the unquestioning acceptance of human error as a normal byproduct of personal effort.

However, the “Zero Defects” concept didn’t gain widespread popularity until it was promoted by Philip B. Crosby in his book “Quality is Free” (1979). Crosby is credited with having developed the “Zero Defects” concept during the early ‘60s while working at the Martin Company as the quality control manager overseeing the Pershing missile program.

The “Zero Defects” concept is diametrically opposed to the philosophy and teachings of W. Edwards Deming, who repeatedly explained that, no matter how vigilant the employees, every process contains inherent (i.e., natural “Common Cause”) variations resulting in defects.

This was most popularly demonstrated through Deming’s “Red Bead Experiment”. In fact, point 10 of Deming's 14 points specifically rejects the “Zero Defects” concept, stating:

Eliminate slogans, exhortations, and targets for the work force asking for zero defects and new levels of productivity. Such exhortations only create adversarial relationships, as the bulk of the causes of low quality and low productivity belong to the system and thus lie beyond the power of the workforce.

When performing causal analysis, we must be able to identify and link an “assignable cause” to a problem in order to have a “root cause”. “Assignable Causes” can often be eliminated (e.g., through corrective action). However, when unable to identify and clearly link an “assignable cause” to a problem, we must recognize and acknowledge that those variations are most likely inherent to the process and cannot be eliminated; without completely re-engineering that process. And re-engineering a process may be cost-prohibitive… or impossible (e.g., due to technical constraints/limitations). However, there are usually risk controls we can institute to mitigate the likelihood/probability and/or consequences/impacts of these problems to an acceptable risk tolerance level.

Ultimately, the “Zero Defects” management approach should have been abandoned long ago. Unfortunately, this delusional concept has persisted well into the 21^st century!

AS 9100, sec. 8.7.1 promotes “Zero Defects” through requiring:

The organization’s nonconformity control process shall be maintained as documented information including the provisions for:
− defining corrective actions for nonconforming products and services detected after delivery, as appropriate to their impacts (see 10.2).

And both ISO 9001 & AS 9100, sec. 9.2.2e promotes “Zero Defects” through requiring:

9.2.2 The organization shall:
e. take appropriate correction and corrective actions without undue delay;

Ultimately, there are two conditions in which the writers of ISO 9001 or AS 9100 consider a “zero defects” approach to always be taken… without consideration to the contribution of common cause variations in a process. These are:

1. Where nonconforming product has been delivered (AS 9100)
2. Where nonconformities are identified during an internal audit (both ISO 9001 & AS 9100)

This leads companies into a never ending game of “Corrective- Action Whac-A-Mole”.