Reliability and Risk Management Essentials for the ASQ CQE
Reliability asks how long a product performs without failing, and risk management asks what could go wrong. Both are woven through the CQE exam.
Quality asks whether a product meets requirements today; reliability asks whether it will keep meeting them tomorrow, and the day after, under real conditions. Risk management ties the two together by asking what could go wrong and how much it would matter. The current CQE Body of Knowledge integrates risk-based thinking throughout, so these concepts appear in more places than candidates expect.
I am John Lee of Alpha Training and Consulting. This guide covers the reliability and risk fundamentals a CQE candidate needs—enough to answer the exam questions confidently without the full depth of a reliability specialist.
What reliability actually means
Reliability has a precise definition: the probability that an item will perform its intended function for a stated period of time under stated operating conditions. Every part of that definition matters—a function, a time period, and a set of conditions. Change the conditions and the reliability changes with them.
The bathtub curve
The most recognizable model in reliability is the bathtub curve, which plots failure rate against time across three phases.
| Phase | Failure rate | Typical cause |
|---|---|---|
| Infant mortality | High but decreasing | Manufacturing defects, weak components |
| Useful life | Low and roughly constant | Random failures |
| Wear-out | Increasing | Fatigue, corrosion, aging |
Reliability metrics you should know
- MTBF (mean time between failures): average time between failures of a repairable system.
- MTTF (mean time to failure): average life of a non-repairable item.
- Failure rate (lambda): failures per unit time, often the reciprocal of MTBF during useful life.
- Availability: the proportion of time a system is operational and ready for use.
Risk-based thinking across the Body of Knowledge
Rather than confining risk to a single chapter, the modern CQE weaves it throughout: FMEA in design and process control, risk-based sampling decisions, risk in quality planning, and risk-based auditing. The tools you have already studied—FMEA, control charts, capability analysis—are all instruments for identifying and reducing risk. Reliability and risk management are best understood as the lens that connects them.
If reliability fascinates you, it may be worth exploring how the CQE compares to the dedicated Certified Reliability Engineer credential—a comparison we cover in a separate article.
Frequently asked questions
What is the bathtub curve?+
A model of the failure rate over a product’s life. It starts high (infant mortality from defects), drops to a low, roughly constant rate during useful life, then rises again as components wear out—forming a bathtub shape.
What is the difference between MTBF and MTTF?+
MTBF (mean time between failures) applies to repairable systems and measures average time between failures. MTTF (mean time to failure) applies to non-repairable items and measures average time until the single failure that ends the item’s life.
How much reliability is on the CQE compared with the CRE?+
The CQE covers reliability at a working level as part of risk and quantitative methods. The Certified Reliability Engineer (CRE) treats reliability as its entire focus and goes far deeper. Our CQE-versus-CRE comparison explains which credential fits your goals.
Written by
John Lee
President, Alpha Training and Consulting
John Lee has more than 25 years of experience in quality engineering and has personally earned every ASQ certification, including the Certified Quality Engineer (CQE). A Shingo Award–winning author, he has helped thousands of engineers pass their ASQ exams on the first attempt with a 94% first-time pass rate.
Certifications: BSME, MBA, CMQ/OE, CQE, CRE, CQA, CQIA, CQI, CCT, CQPA, CQT, CHA, CBA, CSQE, CSQP, CCQM, CSSYB, CSSGB, CSSBB, CPGP, CMBB
Alpha Training and Consulting is an independent training provider and is not affiliated with, endorsed by, or sponsored by ASQ. "ASQ" and "Certified Quality Engineer (CQE)" are trademarks of the American Society for Quality. Exam policies, fees, and Body of Knowledge weightings are set by ASQ and can change—always confirm current details at asq.org.