The Risk Priority Number (RPN) is the product of the Severity (S), Occurrence (O), and Detection (D) ratings.
RPN = (S) x (O) x (D)
Remember, ratings and RPN numbers, in themselves, have no value or meaning.
Ratings and RPN numbers should be used only to prioritize the potential design weaknesses (root causes) for consideration of possible design actions to reduce criticality and/or to make the design more robust (less sensitive to manufacturing variation).
