What is the formula for determining the Risk Priority Number (RPN) in an FMEA?

The formula for determining the Risk Priority Number (RPN) in a Failure Modes and Effects Analysis (FMEA) is indeed calculated by multiplying three key factors: Severity (S), Occurrence (O), and Detection (D). This multiplication approach highlights how risk is evaluated by considering the severity of the potential failure, how often it might occur, and how likely it is to be detected before it causes harm.

By using the formula S x O x D, you are effectively assigning a numerical value to each of these factors and combining them to generate a comprehensive risk score. The higher the RPN, the greater the risk and priority for addressing the failure mode. This allows teams to focus on the most critical issues that could affect product quality and reliability.

In contrast, the other formulas do not accurately represent the relationships among the factors that contribute to risk in the context of FMEA. For example, adding the factors, subtracting them, or dividing them would not reflect the multiplicative nature of risk management, thereby undermining the objective of prioritizing risks effectively and efficiently. This is why the correct formulation relies on multiplication, ensuring that all three factors contribute to the final RPN in a way that aligns with risk assessment methodologies.