ASQ CRE Exam (Certified Reliability Engineer
Exam ) – Accurate Answers To All Questions
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Terms in this set (300)
Reliability Probability that a product/system performs its
intended function for a specified time under stated
conditions.
MTBF (Mean Time Between Failures) Average time between failures for repairable items;
measures time between successful operation cycles.
MTTF (Mean Time To Failure) Average time to failure for nonrepairable items; after
failure the item is not repaired.
MTTR (Mean Time To Repair) Average time needed to restore function after a
failure.
Availability Fraction of time a system is operational: A =
MTBF/(MTBF+MTTR) for steady-state repairable
systems.
Failure Rate (λ) Frequency of failures per unit time; for exponential
distribution λ is constant.
Bathtub Curve Failure rate vs time with phases: infant mortality →
random (useful life) → wear‑out.
Infant Mortality Early-life failures due to manufacturing defects or
weak parts.
Useful Life Period with approximately constant hazard rate.
,Wear‑Out Late-life period where degradation causes increasing
hazard rate.
Maintainability Ease and speed of maintenance actions; commonly
measured by MTTR.
Service Interval Planned time between preventive maintenance tasks.
Corrective Action Action taken after a failure to restore function and
remove root cause.
Preventive Action Proactive steps to prevent potential failures from
occurring.
CAPA Corrective and Preventive Action: closed-loop
approach to address failures and prevent recurrence.
Root Cause Analysis (RCA) "Systematic method to identify the fundamental
cause of a failure (e.g., 5 Whys, Ishikawa)."
5 Whys Ask 'Why?' sequentially to drill down to the root
cause.
Ishikawa Diagram Cause-and-effect (fishbone) diagram organizing
potential causes by categories.
FMEA "Failure Modes and Effects Analysis: identifies failure
modes, causes, effects, controls."
FMECA FMEA with criticality analysis to prioritize risks.
RPN Risk Priority Number = Severity × Occurrence ×
Detection (traditional FMEA scoring).
Common Cause Failure Multiple components fail due to a shared underlying
cause (not independent).
, Reliability Block Diagram (RBD) Graphical model combining component reliabilities
to compute system reliability.
Series System All components must function; system reliability is
product of component reliabilities.
Parallel System System succeeds if at least one path works; reliability
improves via redundancy.
K‑of‑N Redundancy System works if at least K of N components are
operational.
Hot Redundancy Backup component powered and operating.
Cold Redundancy Backup component powered off until needed.
Warm Redundancy Backup component partially powered/ready to take
over.
Human Factors "Consideration of user interaction, ergonomics, and
error likelihood in reliability."
Derating Operate components below rated stress to increase
reliability margin.
Design Margin Extra capability built into design to handle variability
and uncertainty.
Environmental Stressors "External conditions (temperature, humidity, vibration,
shock, ESD) affecting reliability."
Field Data Reliability/maintenance data collected from actual
usage environments.
Warranty Data Service records used to assess early-life reliability
and customer impact.
Exam ) – Accurate Answers To All Questions
Save Groups
Terms in this set (300)
Reliability Probability that a product/system performs its
intended function for a specified time under stated
conditions.
MTBF (Mean Time Between Failures) Average time between failures for repairable items;
measures time between successful operation cycles.
MTTF (Mean Time To Failure) Average time to failure for nonrepairable items; after
failure the item is not repaired.
MTTR (Mean Time To Repair) Average time needed to restore function after a
failure.
Availability Fraction of time a system is operational: A =
MTBF/(MTBF+MTTR) for steady-state repairable
systems.
Failure Rate (λ) Frequency of failures per unit time; for exponential
distribution λ is constant.
Bathtub Curve Failure rate vs time with phases: infant mortality →
random (useful life) → wear‑out.
Infant Mortality Early-life failures due to manufacturing defects or
weak parts.
Useful Life Period with approximately constant hazard rate.
,Wear‑Out Late-life period where degradation causes increasing
hazard rate.
Maintainability Ease and speed of maintenance actions; commonly
measured by MTTR.
Service Interval Planned time between preventive maintenance tasks.
Corrective Action Action taken after a failure to restore function and
remove root cause.
Preventive Action Proactive steps to prevent potential failures from
occurring.
CAPA Corrective and Preventive Action: closed-loop
approach to address failures and prevent recurrence.
Root Cause Analysis (RCA) "Systematic method to identify the fundamental
cause of a failure (e.g., 5 Whys, Ishikawa)."
5 Whys Ask 'Why?' sequentially to drill down to the root
cause.
Ishikawa Diagram Cause-and-effect (fishbone) diagram organizing
potential causes by categories.
FMEA "Failure Modes and Effects Analysis: identifies failure
modes, causes, effects, controls."
FMECA FMEA with criticality analysis to prioritize risks.
RPN Risk Priority Number = Severity × Occurrence ×
Detection (traditional FMEA scoring).
Common Cause Failure Multiple components fail due to a shared underlying
cause (not independent).
, Reliability Block Diagram (RBD) Graphical model combining component reliabilities
to compute system reliability.
Series System All components must function; system reliability is
product of component reliabilities.
Parallel System System succeeds if at least one path works; reliability
improves via redundancy.
K‑of‑N Redundancy System works if at least K of N components are
operational.
Hot Redundancy Backup component powered and operating.
Cold Redundancy Backup component powered off until needed.
Warm Redundancy Backup component partially powered/ready to take
over.
Human Factors "Consideration of user interaction, ergonomics, and
error likelihood in reliability."
Derating Operate components below rated stress to increase
reliability margin.
Design Margin Extra capability built into design to handle variability
and uncertainty.
Environmental Stressors "External conditions (temperature, humidity, vibration,
shock, ESD) affecting reliability."
Field Data Reliability/maintenance data collected from actual
usage environments.
Warranty Data Service records used to assess early-life reliability
and customer impact.
