Page 359 - The Handbook for Quality Management a Complete Guide to Operational Excellence

346 C o n t i n u o u s I m p r o v e m e n t I m p r o v e / D e s i g n S t a g e 347

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

Table 16.1 Severity, Occurrence, and Detectability Levels

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