The severity applies to the EFFECT only. The effect of a given failure will not change unless you change the design of the system or part. In the parachute example, if the chute doesn't open, you probably die and therefore it is a 10 (failure occurs without warning). No suppose I design a smartchute that has built in diagnostics that emits a loud audible alarm telling me it is not going to open...It still doesn't open, but warns me that I am about to die, therefore making it a 9 (failure occurs with warning.) If I take it a step further, and add a smaller backup chute that deploys, that allows me to land without dying, I can make a case for the severity being a 7 (Item operable, but at a reduced level of performance. Customer dissatisfied).
Corrective Action should be first directed at the highest concerns as rank ordered by RPN.
The intent of any recommended action is to reduce the occurrence, severity and/or detection rankings.
If no actions are recommended for a specific cause, then this should be indicated.
Only a design revision can bring about a reduction in the severity ranking.
To reduce the probability of occurrence, process and/or specification revisions are required.
To increase the probability of detection, process control and/or inspection changes are required. Improving detection controls is typically costly. The emphasis should be placed on preventing, rather than detecting, defects.