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Prep notes for ASQ Certified Reliability Engineer exam ISSN 2165-8633
The CRE Preparation Notes series provides you with short practical tutorials on all the elements that make up the ASQ CRE body of knowledge. The articles provide introductory material, basics, how-tos, examples, and practical use guidance for the full range of reliability engineering concepts, terms, tools, and practices.
Keep your knowledge fresh by regularly reviewing topics and tools that make up reliability engineering.
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You will find the most recent tutorials in reverse chronological order below.
We previously looked at reliability requirements and targets, and where the numbers behind them often come from. Before those numbers are defined, however, there is a more fundamental question to consider:
What outcomes is reliability actually intended to support?
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Reliability requirements are often treated as if they simply exist as numbers in a specification, contract or statement of work.
In reality, every reliability requirement comes from a set of assumptions, trade-offs and constraints, whether those are explicitly recognised or not.
Reliability engineering has a shared language, but not always a shared understanding. Terms are often used loosely or interchangeably, particularly in cross-functional teams.
It would obviously be impractical to cover every term here. From experience however, a few distinctions often cause confusion.
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Reliability engineering rarely happens in isolation. More often, it sits within a project environment shaped by cost, schedule, scope and competing priorities.
In many projects, reliability engineering can be seen primarily as a quantitative exercise that is applied once evidence is needed to validate a design. By then, the opportunity to influence architecture, technology choices, or support concepts may be limited.
The greatest impact of reliability engineering often comes much earlier, through structured questioning and risk-informed thinking. Helping teams recognise that reliability engineering influences design and decision-making throughout the project, not just when evidence is required, is part of the reliability engineer’s contribution within a project environment.
Performance monitoring is often where reliability intent meets operational reality and where many well-intentioned reliability programmes quietly lose focus.
Most organisations monitor something, such as failures, availability, response times or costs. The challenge is choosing indicators that genuinely reflect system performance, rather than those that are simply easy to collect or report.
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Supplier reliability is often treated as something that can be contracted out. When systems fail, the instinct is to point to the supplier, the specification, the warranty, or the contract. In practice, reliability is rarely owned by one party alone.
Suppliers design, build and deliver products, but customers define requirements, operating context, acceptance criteria and support concepts. Reliability outcomes sit in the space between those responsibilities.
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When people hear ethics, they often think of formal codes of conduct, professional standards, or exam topics. In reliability engineering, ethics is usually much more practical – and sometimes uncomfortable.
Ethical issues rarely present themselves as clear right or wrong decisions. They tend to appear as trade-offs, pressures and grey areas, often under time, cost or schedule constraints.
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The role of the reliability engineer is often associated with specific activities or phases of the lifecycle, such as prediction during design, testing during development or data analysis in-service. In practice, reliability engineering is a through-life responsibility, even though its focus changes over time.
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Reliability engineering is viewed by many as a technical discipline focused on analysis, modelling, and prediction. While those skills matter, they are only part of the role.
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Reliability, safety, and quality are commonly considered separate disciplines, each with their own people, processes and tools. In practice, they are deeply interconnected and decisions made in one area almost always influence the others, particularly once systems are in service.
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Reliability, Availability and Maintainability are often discussed together. While closely related in practice, they are not the same thing and the distinctions are not always well understood.
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Many people associate reliability engineering with metrics, and while they can be helpful when used correctly, they are not the primary benefit of reliability engineering. The real value lies in the thinking and decisions that shape those numbers.
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When people hear the word reliability, it’s often interpreted as meaning “zero failures”. While that’s understandable, it’s not what reliability engineering is really about.
The Certified Reliability Engineer (CRE) Body of Knowledge, produced by the American Society for Quality, defines reliability as:
“The probability that an item will perform a required function without failure under stated conditions for a specified period of time”
Crucially, each part of this definition needs to be clearly understood and agreed from the outset, particularly between customers and suppliers. Many reliability problems arise not because the definition itself is wrong, but because these elements are interpreted differently.
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When working with a team creating a new system, I always ask, “what is the goal?” The answers often do not make much sense. The team using SMART reliability goals are astonishingly well-stated.
The difference that makes a goal, objective, or requirement practical and useful is summed up by SMART. A SMART goal is Specific, Measurable, Achievable, Relevant, and Time-bound. Let’s explore each element as related to a reliability goal.
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One of the very first plots to do with a string of data is a simple run plot. This plot provides information related to location, trends, patterns, and anomalies, The plot of the data over time is a rather informative chart.
You have most likely constructed many run charts; if not you really should. This short introduction to the run chart will cover creating and interpreting them. Plus we’ll mention a few cautions and tips, as well. [Read more…]
