There are many definitions of quality. Some define quality as ‘conformance to requirements’. Others define quality as merely ‘meeting customer specifications’. When the mentality is to focus on the most marginally-accepted product or service (focusing on either the upper or the lower specification, or both), it isn’t as competitive as focusing on the most ideal product target.

This author defines quality as: Product uniformity around a target value(s). The target might be a larger-is-better quality characteristic or a smaller-is-better quality characteristic. It might also be a nominal-is-best where some named value is the target. With any of these quality characteristics, it is important that there is relentless attention paid to having as little variation around the target values as possible, or competitive.

Use: The definition of quality is important because it provides the philosophy toward process improvement.  If you have ever heard of the expression “close enough for government work”, this mentality is not competitive. Perhaps you have heard of the expression “fitness-for-use”. Again, with this way of thinking the organization is only focusing on the most marginally-accepted product and not the target that the engineer or the customer had in mind.

Six Sigma Terminology