Page 119 - The Six Sigma Project Planner

Table 6. FMEA Severity, Likelihood, Detectability Rating Guidelines
Note: p is the estimated probability of failure not being detected.

Severity Occurrence Detectability
(SEV) (OCC) (DET)
Rating How significant is this How likely is the cause of How likely is it that the

failure’s effect to the
the cause, if the defect
customer? this failure to occur? existing system will detect
occurs?
1 Minor. Customer won’t Not likely. Nearly certain to detect
notice the effect or will before reaching the
consider it insignificant. customer.
(p ≈ 0)
2 Customer will notice the Documented low failure Extremely low probability
effect. rate. of reaching the customer
without detection.
(0 < p > 0.01)
3 Customer will become Undocumented low failure Low probability of
irritated at reduced rate. reaching the customer
performance. without detection.
(0.01 < p > 0.05)
4 Marginal. Customer Failures occur from time to Likely to be detected
dissatisfaction due to time. before reaching the
reduced performance. customer.
(0.05 < p > 0.20)
5 Customer’s productivity is Documented moderate Might be detected before
reduced. failure rate. reaching the customer.
(0.20 < p > 0.50)
6 Customer will complain. Undocumented moderate Unlikely to be detected
Repair or return likely. failure rate. before reaching the
Increased internal costs customer.
(scrap, rework, etc.). (0.50 < p > 0.70)
7 Critical. Reduced Documented high failure Highly unlikely to detect
customer loyalty. Internal rate. before reaching the
operations adversely customer.
impacted. (0.70 < p > 0.90)
8 Complete loss of Undocumented high failure Poor chance of detection.
customer goodwill. Internal rate. (0.90 < p > 0.95)
operations disrupted.
9 Customer or employee Failures common. Extremely poor chance of
safety compromised. detection.
Regulatory compliance (0.95 < p > 0.99)
questionable.
10 Catastrophic. Customer or Failures nearly always Nearly certain that failure
employee endangered occur. won’t be detected.
without warning. Violation (p ≈ 1)
of law or regulation.

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