Current Risk Assessment

Severity 1–10

Occurrence 1–10

Detection 1–10

Higher means harder to detect.

Action Threshold RPN

Planned Actions After improvement

Occurrence After Action 1–10

Detection After Action 1–10

Risk Priority Number

— RPN

Severity times occurrence times detection

Risk & Action Value

Criticality: — S×O
RPN After Actions: — RPN
Risk Reduction: — %
Margin Over Threshold: — RPN
RPN if Only Detection Improves: — RPN
RPN if Only Occurrence Improves: — RPN

RPN multiplies ordinal ratings as though they were measurements, which they are not — a severity of 8 is not twice a 4, so the product has no physical meaning and identical RPNs can represent very different risks. Newer FMEA practice has largely replaced RPN with an action priority table precisely because of this, and a high severity should trigger action regardless of how low the product is. Use the number to rank a list, never to decide that a risk is acceptable. Improving detection also does nothing to prevent the failure: it catches defects that were still made, and where severity is high, occurrence is the only honest lever.

Product Risk & Critical-to-Quality FMEA Matrix — free, with the formula and a worked example, at Textile School.