In FMEA, what does the Risk Priority Number (RPN) represent and how is it calculated?

• A. A combined risk score calculated as Severity × Occurrence × Detection.
• B. The probability of a failure occurring in the next production run.
• C. The expected time to detect a failure in the process.
• D. The overall cost impact of a failure.

Answer: (A)

In FMEA, the RPN is a single number used to prioritize which failure modes to address, based on three dimensions of risk: how severe the effect would be, how often the failure could occur, and how well current controls can detect it before it reaches the customer. Each dimension is rated on a scale (commonly 1 to 10), where higher numbers indicate greater severity, higher likelihood of occurrence, or weaker detection. The Risk Priority Number is the product of these three ratings: Severity × Occurrence × Detection. Because it multiplies all three factors, a high severity, even with moderate occurrence and poor detection, can yield a high RPN, guiding you to prioritize that failure mode for improvement. This is why the option describing a combined risk score calculated by multiplying Severity, Occurrence, and Detection best captures what the RPN represents. The other descriptions—probability of a failure in the next run, time to detect a failure, or overall cost impact—don’t reflect the three-factor, multiplicative nature of RPN.