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Mar 11, 2010

Statistical Process Control (SPC)

SPC: Doing It Right the First Time

To prosper in the economic climate of today, companies and their suppliers must be dedicated to never-ending improvement in quality and productivity. Leaders must constantly search for more efficient ways to produce products and services that meet customers' needs. Most organizations clearly state their dedication to achieve continual quality improve­ment with the company's Quality Policy.


Most everyone agrees that "Doing it right the first time" and the policy of prevention are sensible and even obvious philosophies which will, when adopted, improve the quality of all the products manufactured or services provided by any company. Quantitative measures are needed to effectively monitor process and product or service performance. Statistical Process Control or SPC and its associated problem solving techniques contain the quantitative tools which will allow us to get a more objective handle on quality. These concepts have been taught under the banner of SPC, Statistical Methods and most recently the Six Sigma approach. All of these are based on simple statistical methods that can help manage process variability and thus improve quality.

SPC: The Definition

You may or may not have an idea of what SPC or Statistical Process Control is. In either case, let's see what it is not. It has already been said that it is not a quick fix for quality or productivity problems. Neither is it simply learning about control charting. Instead, it is a way of managing business operations to achieve continuing improvement in both process and people. Often SPC has been misunderstood to be simply using statistics to try to solve business problems.

SPC can be defined as using statistical techniques to analyze data, then using the information to achieve predictability from a process.

SPC is a technique of monitoring and measuring performance using basic statistics such as averages, ranges or standard deviation along with the associated time sequenced charts and graphs. SPC methods can provide a picture that can be analyzed to detect an oncoming problem before the product of a process goes off specifications. Further, the data and charts can be analyzed to help identify the root cause of a problem--the first step toward problem elimination and prevention

SPC: The Beginnings

SPC is neither a new technique nor was it developed by the Japanese as many suppose. To review the development of SPC requires that we discuss Dr. W. Edwards Deming, who could be considered the "father of SPC".

Dr. Deming, a statistician by education, was associated with the Census Bureau, National Bureau of Standards and the Department of Agriculture early in his career. He became acquainted with Dr. Walter Shewhart of Bell Labs who introduced him to the concepts of process control.

During World War II, Dr. Deming taught statistics to thousands of individuals from hundreds of companies. The objective was to use this knowledge to bring better precision and more productivity to the nation's wartime manufacturers. A serious shortcoming of this effort was that it failed to involve top management but focused primarily on the engineering functions. Gradually, the techni­ques, though initially effective, disappeared due to lack of manage­ment support.

In 1945, Dr. Deming assisted Japan in certain agricultural areas. Later he was invited to teach statistical methods to industry. Through the efforts of Ichico Ishikawa, Japanese managers became not only familiar with, but committed to the concepts taught by Dr. Deming. Change was not immediate, but as you know, Japan now sets the standard for quality in many industries. Dr. Deming has since been honored by the Japanese for his efforts. Their highest award for industrial excellence is known as the Deming Prize.

Today many managers still think that only minor changes in their organizations will solve productivity and quality problems. There are numerous productivity programs available, but many avoid the recognition of the responsibility of management to change the systems they perpetuate.

Deming once asserted that 85 percent of all the problems of a company belong to the system which only management can change, and 15 percent of the problems can be solved by the workers. Before his death in 1994, he revised his estimates to 94% and 6%. If a company is to achieve significant gains in productivity, the management methods and styles of the organization must change.

SPC: Benefits

Successful implementation of the SPC approach to the control of quality offers several benefits:

l. Increased customer satisfaction by producing a more trouble-free product.

2. Decreased scrap, rework and inspection costs by controlling the process.

3. Decreased operating costs by optimizing the frequency of process adjustments and changes.

4. Maximized productivity by identifying and eliminating the causes of out of control conditions.

5. A predictable and consistent level of quality.

6. Elimination or reduction of receiving inspection by the customer.

The challenge is to learn and use the tools of SPC properly. The rewards are great. Only by everyone in the organization working together toward the same quality goal can your business ultimately be successful in the market place.
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