victorpapa,
Not a stupid question, in fact very pertinent as to concerns over how these probability calculations are done.
If you do a calculation prior to entry into service, then in operation there is an occurrance and you take some form of corrective action, followed by another probability assessment, can you now discount that occurrance (as some seem to believe) when recalculating probability ?
Or, in simpler terms, if something happens, and you fix it, but it happens again, (either due to the same or different cause/s), do all the flags start to go up, or can you say I'll fix it and continue on with the same level of probability as prior to the occurrance ?