Applied Statistics and Probability for Engineers

642 CHAPTER 16 STATISTICAL QUALITY CONTROL

when the business is in trouble and later abandoned. Quality improvement must become part

of the culture of the organization.

The control chart is an important tool for process improvement. Processes do not natu-

rally operate in an in-control state, and the use of control charts is an important step that must

be taken early in an SPC program to eliminate assignable causes, reduce process variability,

and stabilize process performance. To improve quality and productivity, we must begin to

manage with facts and data, and not just rely on judgment. Control charts are an important part

of this change in management approach.

In implementing a company-wide SPC program, we have found that the following ele-

ments are usually present in all successful efforts:

1. Management leadership


2. A team approach


3. Education of employees at all levels


4. Emphasis on continuous improvement


5. A mechanism for recognizing success

We cannot overemphasize the importance of management leadership and the team approach.

Successful quality improvement is a “top-down” management-driven activity. It is also im-

portant to measure progress and success and to spread knowledge of this success throughout

the organization. When successful improvements are communicated throughout the company,

this can provide motivation and incentive to improve other processes and to make continuous

improvement a normal part of the way of doing business.

The philosophy of W. Edwards Demingprovides an important framework for imple-

menting quality and productivity improvement. Deming’s philosophy is summarized in his 14

points for management. The adherence to these management principles has been an important

factor in Japan’s industrial success and continues to be the catalyst in that nation’s quality- and

productivity-improvement efforts. This philosophy has also now spread rapidly in the West.

Deming’s 14 pointsare as follows.

1. Create a constancy of purpose focused on the improvement of products and serv-
   ices.Constantly try to improve product design and performance. Investment in re-
   search, development, and innovation will have a long-term payback to the organization.


2. Adopt a new philosophy of rejecting poor workmanship, defective products, or
   bad service.It costs as much to produce a defective unit as it does to produce a
   good one (and sometimes more). The cost of dealing with scrap, rework, and other
   losses created by defectives is an enormous drain on company resources.


3. Do not rely on mass inspection to “control” quality.All inspection can do is sort
   out defectives, and at this point it is too late because we have already paid to pro-
   duce these defectives. Inspection occurs too late in the process, it is expensive, and
   it is often ineffective. Quality results from the prevention of defectives through
   process improvement, not inspection.


4. Do not award business to suppliers on the basis of price alone, but also consider
   quality.Price is a meaningful measure of a supplier’s product only if it is consid-
   ered in relation to a measure of quality. In other words, the total cost of the item
   must be considered, not just the purchase price. When quality is considered, the
   lowest bidder is frequently not the low-cost supplier. Preference should be given to
   suppliers who use modern methods of quality improvement in their business and
   who can demonstrate process control and capability.

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