Some developers use Reliability and Quality interchangeably; however, there is a demonstrable difference between these two disciplines. Reliability defines goals and performs predictive tests of the functionality of a product over its lifetime, whereas Quality is concerned with the action of a quality at one point in time. As stated in the definitions, Reliability assures, through predictive testing, that a product functions without failure for a desired period during it’s lifetime under defined conditions of use, whereas Quality assures conformance to product and process goals.

However, Reliability is very dependent on Quality. For example if poor QC allows manufacturing variances in product components, subsystems and production processes beyond the established QC guidelines, then this variance will quite likely lead to poorer reliability.



A product developer’s point-of-view of Quality and Reliability necessarily stems from the domain in which product developers perceive, perform and have responsibility. Through their PD-colored glasses, the PD discipline:

• Requests and helps develop specific requirements to which a product can be designed and technically implemented,
• Requires goals to which a product’s qualities and functionality can be tested,
• Requires testable or assessable goals and variance around the goals that can be validated through testing.

Here’s what Quality needs to provide - We developers need to have in hand the list of claims advocated by the group of stakeholders for the product. These claims, or qualities, must have measurable or assessable, but 100% agreeable, targets (within agreeable variances) so that we can design and test the product without ambiguity. Note that it is these same qualities that will be further tested by Quality Engineers through QC methods (as guided by QA).