As I understand correctly, there are differing opinions around the ranking scale of 1-10 vs 1-5 vs no numbers, whether to multiple the values or use the face value (9x3x5=135 vs 3x9x5=135, or 935 vs 395), and that there is (or is in the works) a change coming removing RPN and replacing it with Action Priority H-M-L. My question is specific to the Severity value. I had read a while back (sorry, I don't recall where) that ALL Possible/Potential Effects on Failure should use the Highest Severity score when calculating the RPN for ALL Effects, Causes & Controls within a single Potential Failure Mode. Assuming I want to keep my current 1-10 scale and then use the new Action Priority H-M-L process (specifically the PFMEA Action Priority Logic - thank you Andy Nichols for this!), is it correct to determine the total SOD value by using the HIGHEST Severity Value within the failure group? Or should each effect, cause & control be individually determined? I've attached a screen shot of my Excel PFMEA template that I've been using which I'm in the middle of modifying to remove RPN and replace with Action Priority. Using the dummy info shown, 10 is my max Severity value for ALL potential effects on failure (for the first Potential Failure Mode) and is therefore used for all 10 RPN (now AP) calculations to determine the H-M-L Action Priority. (I hope I'm making sense here - sorry, this is somewhat difficult for me to explain since I'm fairly new to this). So currently my SOD scores are 10-9-3=HIGH, 10-8-4=HIGH, 10-7-5=HIGH, 10-6-3=HIGH, 10-5-4=MEDIUM and so on (always using 10 for the first Potential Failure Mode). The point being that Severity is 10 for ALL Potential Effects on Failure for the first listed Potential Failure Mode. Severity could be different for the next Potential Failure Mode (which I have shown as 2-9-2=HIGH in the screen shot). I'm trying to keep this simple and don't want to open up a debate - I would just like to get clarification around whether you're supposed to use 10x9x3, 10x8x4, 10x7x5 and so on OR if 9x9x3, 7x8x4, 5x7x5 and so on. Which method is correct? For RPN? For AP? Or Both?