In quality tables and in discussions of QFD, the terms quality characteristic and quality element are often used interchangeably, which causes many people to ask me what the difference between the two is.
The term quality characteristic has been defined by Japanese Industrial Standards (JIS), and the term as used in QFD is identical in meaning to the term used in quality assurance. The term quality element as used in QFD refers to a higher, more abstract level of meaning that includes quality characteristics but can also be thought of as a standard to be used in evaluating quality.
The reason that I began using the term quality element in addition to the term quality characteristic was to eliminate some of the inconvenience associated with determining quantitative measurement and units for use in the extraction of quality characteristics.
When dealing with the service industry, especially, the extraction of elements that can be considered quality characteristics enables the creation of quality tables, even in cases where measurement methodology is unclear. Thinking of quantifiable, concrete quality characteristics after you have created a quality table and identified the critical quality elements is a much more efficient way of working, I feel.
Applying this idea to general QFD is a good way to improve efficiency during quality deployment. It is always easiest to have concrete quality characteristics to extract, but extracting quality elements and then thinking of ways to quantify them once their importance has been realized is also an efficient way to approach the process.
If you are not sure whether an item is a quality characteristic or a quality element, first think about whether or not it is quantifiable. For example, in Diagram 10.1 we can see that it is not possible to quantify the quality of reliability. Mean time to failure (MTTF) and mean time to recovery (MTTR), on the other hand, can be expressed in terms of time and can be quantified in units of minutes or hours.
When establishing design quality, it is possible to specify an MTTF in units of hours but it is not possible to specify reliability as a quantity. Once quality elements are extracted and their importance recognized, it then becomes possible to determine a quality characteristic that can be specified in concrete terms.
- JIS definition of quality characteristic: Properties and performance levels used to evaluate quality.
- Quality element: a property that can be used as a standard in evaluating the quality
4M Analysis Process
The purpose of this procedure is to define the steps to do a 4M …
