What is Quality? Quality Defined

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What is Quality?

Credit: flickr: Particularly Everything

In the 35+ years since our founding, we’ve detailed the concepts of quality and SPC to a great degree. However, it’s important from time to time to remind ourselves just what is quality and why is it important.

Before we can control quality, we need to understand what the word “quality” means. Quality, like beauty, is in the eye of the beholder. Each of us judges the quality of many items every day, and we each have a different idea about what quality is for each item. We know what we like or what we want, and what we don’t like or want. How we determine the quality of an item depends on both our personal preference and our frame of reference for that particular item.

Is cloud-based SPC the place to realize the benefits of quality to your organization?

For example, production workers might see quality as conformance to specifications. If the size of the hole they produce is within their tolerance, it is a good hole. If not, it’s bad. Marketing people might think of quality as something that sells well and causes little trouble for the customer. Supervisors see quality when production is higher than normal and there are few reworks. Customers see quality if the product does what they expect it to do without any breakdowns.


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So what are some points upon which we can all agree equate to quality?

  • Quality is conformance to specification. 

This idea comes from labeling parts that are in-spec as good and out-of-spec as bad. Are they really good and bad? No. Somebody has either assigned or negotiated the tolerances and a simple stroke of a pen changing these tolerances can transform bad products into good.

  • Quality is a measure of how good a product is — quality is meeting customer acceptable quality levels.

Does the quality of the product change when you renegotiate the contract with the customer? No, acceptable quality levels are simply tolerances on tolerances. They specify the number of times it is permissible to miss the target by a given amount.

  • Quality is zero defects.

This notion is based on our ability to define a defect. If we define a defect as a part out of spec, then we are right back at “conforming to the specifications.”

  • Quality is the absence of variation.

This is a goal that initially sets many companies’ SPC implementations in motion.

  • Quality is in the eyes of the beholder.

With manufactured products, quality is determined by the customer. If the customer thinks the quality is good, then it’s good. In making the judgment the customer weighs competitive products, cost, performance, and personal preference.

Because we define a product’s quality in relation to competing products, it is a constantly moving target. Finding this target means adjusting to meet the customer’s needs as well as maintaining the competitive edge. This requires never-ending improvement.

We will dig more into this aspect of “What is Quality?”  and what areas are of concern to the most important stakeholder – your customer – in the second part of this series.


This content is from Zontec’s The Book of Statistical Process Control.  You can download a free copy here.