Crosby's Church of "Zero Defects"

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

What is "Zero Defects"

 “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.


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.

Why "Zero Defects" is a flawed concept

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.

Source: When performing “Cause & Effect” analysis, we must be able to identify and link an “assignable cause” to the event (nonconformity). “Assignable Causes” can potentially 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 technological constraints/limitations or even “technical contradictions”). 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, no amount of “cheerleading” or impassioned motivational speeches will ever eliminate human error. Human error is and always has been “a normal byproduct of personal effort”. However, there are steps that companies can take, such as “error-proofing” (Poka Yoke) or removing the human component from a process through a redesign (aka ReEngineering) of the Process OR taking steps to “mitigate” the potential for human errors (e.g., rotating personnel to avoid fatigue).

Delusional attempts to “eliminate” human error through motivational efforts only serve to exacerbate the problem. It is a truly poor reflection on the Quality Profession that such an obviously flawed concept has persisted well into the 21st century!

Only through accepting that human error is a “common cause” variation can we address the problem for what it truly is. Whenever there is a “common cause” variation in a process, we have two options. We can either change the process OR we can implement risk controls (e.g., to mitigate the risk). For example, changing the process to include “error-proofing” (poke yoke) can eliminate human error by eliminating the possibility of an error being introduced. Alternatively, we can greatly reduce the risk of human error being introduced through:

  • Developing better-understood, comprehensive work instructions/procedures
  • Developing more effective training of personnel
  • Ensuring that personnel have the resources needed to perform the work
  • Reducing the number of times that people “touch” or move a product (as every instance that a product is touched or moved increases the risk of a defect error being introduced).

The above list is not intended to be all-inclusive.

"How "Zero Defects" followers view "risk"

Upon being asked about how “risks” relate to “Zero Defects”, a follower of Philip Cosby stated that there are two types of risks. There are “expected risks” (that have not occurred) and “realized risks” (which have occurred). Going to great lengths to avoid recognizing “common cause” variation, this individual explained that “risk mitigation” actions are taken to prevent a risk from occurring. but once a risk has been realized, then corrective action must be taken. This individual completely ignored the lesson from Deming's “Red Bead Experiment”.

"How "Zero Defects" followers view "human factors"

One of the first “Zero Defects” followers I met explained that he had worked at a company that had subscribed to Deming's philosophies… and had focused 100% of their attention on their processes. His complaint was that this company refused to hold people accountable for their actions.

Deming NEVER stated or suggested that companies not hold personnel accountable for their actions. What he emphasized was to not punish workers for process-related nonconformities that are out of the worker's control (i.e., process-related common cause variations). Workers should only be held accountable for actions that are within their personal control (e.g., not following a procedure, failure to monitor and take action when a trend is identified and confirmed).

ISO 9001 & AS 9100... still stuck in the '60s & '70s

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

  1. Where nonconformities are identified during an internal audit (both ISO 9001 & AS 9100, sec. 9.2.2e)
  2. Where nonconforming product has been delivered (AS 9100), sec. 8.7.1

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

Both ISO 9001 & AS 9100, sec. 9.2.2e promotes “Zero Defects” by requiring:

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

And AS 9100, sec. 8.7.1 promotes “Zero Defects” by 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).