Deming's Point Three

Cease dependence on mass inspection.

The third of Dr. W. Edwards Deming's 14 Points for Management reads, "Cease dependence on mass inspection to control quality. Instead, depend on process control through statistical techniques."

♦ Monitor all processes in the system, rather than looking only at after-the-fact test results.

♦ This is a new philosophy.  The right processes must be built into the system, without dependency on tests and inspection.

♦ Inspection to improve quality is too late, ineffective, costly.

♦ Inspection adds no value.  The product is already good or bad by the time we inspect the product.  The enemy is the variation and sources of variation swirling in and around design, development and manufacturing processes.

♦ This is not to say that we must eliminate all inspection.  We'll not have answer to the question, "How are we doing?", without measurement, without assessment.  Deming's warning is about mass inspection -- end-of-the line, AQL-sampling-table-driven, the-defects-are-already-there-or-not, budget-sucking, time-sucking, non-value-adding mass inspection.  Alternatives to mass inspection include:

1.  Trust your operators.  God does not make junk.  Provide them with the measurement technology they need to detect problems at the source.  Once them find them, they'll fix them.

2.  Put more emphasis on the intermediate, analytic statistical methods that Walter Shewhart invented at Bell Laboratories.  They allow us to learn everything we need to know about our processes with small sample subgroups -- no need for mass inspection.

♦ It's far better to improve processes to prevent quality defects.  

♦ Quality comes not from inspection, but from improvement of the production process.  Inspection, scrap, downgrading, deviations and rework are not corrective action on the process.

Q.  Who is responsible for the quality of incoming parts and materials?

A.  Our quality control department.  It is their job to inspect incoming materials and parts and to make sure that nothing goes out our door that is faulty.

Wrong way.


W. Edwards Deming, Out of the Crisis, MIT Center for Advanced Educational Services, Cambridge, MA (1986), pp. 28-31.

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