The Quality Triangle and Reliability

How Does Reliability Fit with the Quality Triangle?

The Quality Triangle provides a method to establish priorities for a project. It strives to balance time, cost, and quality (or scope instead of quality). It does not include reliability.

Now I am a bit bias as a reliability engineer and believe a projects set of priorities should explicitly include reliability performance. Of course, there are many potential priorities, yet reliability certainly can make or break a product, it’s market acceptance, and an organization’s profitability.

So, given a quality triangle based set of priorities, how does reliability fit in?

Reliability as a Subset of Quality

David Garvin suggests there are eight dimensions of product quality. [“Competing on the eight dimensions of quality”. David A. Garvin, Harvard Business review. 1987] Reliability is one such dimension.

The importance or priority of product reliability will depend now which dimensions of quality the team’s leadership deem critical.

Therefore, given a relative ranking of quality vs the other priorities, we need to understand the reliability contribution to achieving quality requirements.

Reliability as a Subset of Scope

The product development triangle, iron triangle, or similar prioritization schemes substitute scope or features for quality. Again, reliability performance in some organization is considers a product feature.

The reliability requirements provides a target or baseline. The reliability requirement is a product specifications like weight, response time or color of the enclosure.

If we would like to improve reliability above the requirement that may be considered an increase in scope of the project. Adding a reliability test, such as an accelerated life test (ALT), may become a discussion around the increase in scope.

Understanding the priority concerning achieving product requirements or the range of solutions the product will address, provides a means to gauge the relative importance of product reliability. Not all requirements or project tasks are equal, thus being able to articulate the value provide by achieving reliability targets is important.

Reliability as a Fourth Leg of the Triangle

As reliability engineers we often focus on reliability. Yet the concept of the Quality Triangle is to establish relative priorities for decision making throughout the product development process.

Product reliability may have a desired target that would meet or exceed customer expectations. If product reliability is too low, it may erode or erase profitability and customer satisfaction. There may be a lower threshold below which the focus may shift to prioritizing reliability performance.

Product reliability impacts development time, product cost, and both the quality and scope aspects of a development program. Reliability tasks such as ALT can be expensive, yet provide invaluable information to inform decision making. Understanding the lower threshold that may threaten the success of the program vs good enough reliability vs achieving product reliability targets permits you to balance reliability improvement investments with the range of other priorities.

Priorities, the Quality Triangle, and Reliability

Each team will make a myriad of decisions. Decision concerning the design and use of a product impact product reliability. Making informed decision concerning reliability while maintaining the appropriate balance with the range of other priorities works to improve reliability performance along with launching a successful product.

How do you balance reliability with other priorities?