Blame Quality Control

The situation

Photo: W. J. Latzko, Ph.D.
W. J. Latzko, Ph.D.
Recently the Wall Street Journal reported on an error that appears to have occurred in the Philadelphia Mint’s production of the new dollar coin. Of the 300 million coins produced by the mints, an estimated 50,000 coins did not have the edge-incised inscription, “In God We Trust”, “E Pluribus Unum”, the year and the mintmark.

“We take this matter seriously. We also consider quality control a high priority. The agency is looking into the matter to determine a possible cause in the manufacturing process”, was a statement from the mint. The Wall Street Journal carried this further by interviewing Mr. Ron Guth, president of Professional Coin Grading Service. Mr. Guth’s opinion was quoted in the Wall Street Journal that, “it appeared from the roughly 50 smooth-edged dollars he has authenticated that the problem had to do with quality control rather than mechanical error.

In my opinion, both Mr. Guth and the Wall Street Journal do not understand the function of quality control. They are falling into a common misconception that when a mistake occurs that it is the fault of the people known as “quality control”.

It is true that some companies call the production functions of checking work—and perhaps correcting it—”Quality Control”. That is NOT quality control in the technical sense. That is a production task called inspection or auditing. There are two issues with this method of assuring quality: (1) it is not failsafe since the auditors (appraisers) miss some bad work and (2) this guarantees that the escape rate of errors remains unchanged. Let us examine these two issues.

Finding all the defects (some call this a non-conformance).

There are two types of inspection: independent and dependent.

In independent inspection, one replicates the work and one compares the two outcomes. For example, many web sites require that you initially enter a password and they require that you enter it a second time. If the two entries agree, the system records the password. If they do not agree, the program generates an error message. Although safer than dependent inspection, in case of disagreement, one knows not which is correct and which is in error.

Dependent inspection requires a second look at the completed work. This is more difficult. By way of illustration take 30 seconds and count the letter S that appears in the following sentence: SHE SELLS SEASHELLS BY THE SEASHORE. It takes a lot to get the right number the first time. Did you see two, three or more? The correct answer is that eight of the letters appear in the sentence.

Dependent inspection is rarely 100% accurate in finding the non-conformance that exists in a mass of work. A more likely number is 80% non-conformances found. Inspection at the mint is of necessity dependent. Could a batch of coins been missed for the second process of inscribing the rim? Certainly, inspectors could miss such an event. Do not blame them. Blame the process that operated with inefficient controls.

The escape rate of errors

If inspection cannot guarantee 100% error free output, what is one to do? The answer lies in working on the process to make it error free. This requires management action and measurement. The measurement tool is the control chart invented by Dr. Walter Shewhart in the 1920’s. The word control was an unfortunate choice on the part of Dr. Shewhart since it implies a police activity. In fact, what he meant by the word was the ability to predict that a stable process will continue at its current level of quality as long as the process remains unchanged.

The finding and removing errors does not improve the process. Dr. W. Edwards Deming used the analogy of a fire. “If there is a fire (errors) in the building (process)”, he used to say, “and you put it out you have not improved the building.” (The writer inserted the parentheses.) Of course, one wants to save a building. It is far more economical to avoid the fire in the first place.

Inspection not only is expensive and less than 100% efficient, it lulls management into a false sense of security. True quality control uses failsafe processes and monitors these for conformance with a control chart.

If a problem happens, don’t blame quality control, blame the people in charge of the process who allowed it to happen, management. Are you listening Wall Street Journal?