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Quality is defined here as the measure of customer delightment. Customer satisfaction is a region on this scale.
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How can we measure quality?
Ohfuji (1995) notes that quality is measured by qualities. Akao (1990) calls these qualities quality characteristics. The whole concept of Quality Function Deployment is based upon the deployment of these qualities.
An entity serves a purpose. We can state that purpose in the form [verb,noun]. In value engineering and in function analysis, a purpose is called a function. In order to eliminate multiple meaning for the word 'function', I shall depart from this practice and use the word 'purpose'. One can associate a measure to a purpose in the form [verb,noun,attribute]. If an attribute is not measurable garcia1 (1990) calls it a quality element. If the attribute is measurable he calls it a quality characteristic. I shall define a qualitie as a measurable purpose measure of the form [verb,noun,attribute].
A familiar purpose of a person is [drive,car]. Familiar qualities are [drive,car,distance], [drive,car,speed], and [drive,car,acceleration]. A less familiar purpose measure is [drive,car,absolute_distance_from_lane_center] which measures the steadiness of our driving. Each of these qualities has a different importance in terms of measuring the quality of our driving.
In the house of quality, the importance measures are assumed to be constant. These measures are determined by a multiple step process. The customer population, in this example, is all persons who might come in contact with our driving of the car. The voice of the customer is obtained, probably through interview, survey, or a focus group, and measured. Typical customer desires might be 'drive within speed limit', 'don't cross center line', 'stop at stop lights', and 'stop for pedestrians crossing'. A group would then correlate the customer desires with the qualities. Finally, the correlation would be used to transform the importance of the customer desires into the importance of the qualities. We now have the importance of the qualities subjectively quantified in terms of the importance of the customer desires.
We deploy the purpose of a product using a purpose and means diagram. To accomplish this, we need to define the means of accomplishing this purpose. Such a deployment might be:
where [monitor,environment], [monitor,instrumentdata], [control,direction], [control,speed], [control,visibility], [control,humancomfort], [control,carhealth] are the means of performing the purpose [drive,car].
If we now form qualities for these means, which are purposes for further deployment, then we have a more refined set of qualities. Examples are [monitor,environment,distance_to_car_in_front], [monitor,instrumentdata,engine_temperature], [control,direction,rate_of_turn], [control,speed,acceleration], [control,visibility,percent_of_windshield_clear], [control,humancomfort,absolute_interior_temperature_less_desired_temperature], and [control,carhealth,speed_over_speedbumps]. Note that these qualities are more representative as measures of what we do when we [drive,car] and of the overall goodness of what we do when we [drive,car].
Suppose we now correlate the customer desires with the lower level purposes. We can then transform the importance of the customer desires to the importance of the lower level purposes. Noting that [monitor,environment,distance_to_car_in_front], [control,visibility,percent_of_windshield_clear], and [control,carhealth,speed_over_speedbumps] all correlate with [control,carhealth] we see that we can correlate each of the purposes with each of the qualities and then transform the importance of the purposes to the importance of the qualities.
Understanding the importance of the qualities, as determined by the customer, helps focus efforts to ensure quality.
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