Question 1

In an FMEA, the Risk Priority Number (RPN) is calculated as:

Accepted Answer

RPN = Severity (S) × Occurrence (O) × Detection (D), each rated 1–10. High RPN scores indicate the highest-priority failure modes requiring corrective action. Note: a high Severity score alone (e.g., S = 10) should also trigger action regardless of RPN, because even rare, detectable failures with catastrophic consequences must be addressed.

Question 2

An FMEA is best used during which phase of DMAIC?

Accepted Answer

FMEA is primarily an Analyse-phase tool for systematically identifying potential failure modes and their causes. It can also be used in the Improve phase to evaluate risks of proposed solutions before implementation, or in the Control phase to build the control plan. It is most commonly associated with the Analyse phase in Six Sigma DMAIC projects.

Question 3

What does the 'Detection' score in an FMEA measure?

Accepted Answer

Detection (D) rates the effectiveness of current controls at catching the failure mode before it escapes to the customer — a score of 1 means the failure is almost certainly detected; a score of 10 means detection is almost impossible. Lower detection scores are better. Improving detection (adding inspection, testing, or poka-yokes) reduces RPN.

Question 4

In FMEA, the Risk Priority Number (RPN) is calculated as:

Accepted Answer

RPN = Severity (S) × Occurrence (O) × Detection (D), each rated on a 1–10 scale. The product identifies which failure modes should be prioritized for corrective action. Higher RPN = greater risk.

Question 5

A failure mode has Severity = 9, Occurrence = 3, Detection = 2. What is its RPN?

Accepted Answer

RPN = 9 × 3 × 2 = 54. Despite the high severity (9), the low occurrence (3) and excellent detection (2) keep the RPN relatively low. Teams often set RPN thresholds (e.g., >100 or >200) to trigger mandatory corrective actions.

Question 6

In FMEA, the 'Detection' rating measures:

Accepted Answer

Detection (D) rates the effectiveness of current controls at detecting the failure mode or its cause before the defect reaches the customer. A rating of 1 = almost certain detection; 10 = no detection capability. Lower detection ratings improve the RPN.

Question 7

What type of FMEA is conducted to analyze failures in a manufacturing or assembly process step?

Accepted Answer

Process FMEA (PFMEA) analyzes potential failure modes in manufacturing or service process steps — machine setup errors, operator mistakes, material handling failures. Design FMEA (DFMEA) focuses on product design failures before the product goes into production.

Question 8

After implementing corrective actions for a high-RPN failure mode, the team should:

Accepted Answer

After implementing corrective actions, the team re-rates Severity, Occurrence, and Detection as appropriate and recalculates the RPN. The goal is to verify the action reduced risk to an acceptable level. Severity ratings typically only change if the design or process fundamentally changes.

Question 9

A severity rating of 10 in FMEA typically represents:

Accepted Answer

In standard FMEA scales, Severity 10 (or 9-10) is reserved for failure modes that affect safety — causing injury, death, or regulatory non-compliance — without warning. These failures demand immediate corrective action regardless of RPN score.

Question 10

What is the primary weakness of relying solely on RPN to prioritize FMEA corrective actions?

Accepted Answer

RPN multiplication can mask critical failures. For example, S=9, O=1, D=1 gives RPN=9 — but Severity 9 represents a safety risk that demands attention regardless of low occurrence. Modern AIAG-VDA FMEA guidance recommends Action Priority (AP) ratings that weight severity more heavily than RPN.

FMEA & Risk Analysis Practice Questions

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