I am simulating a process in Arena software. One part of the process has a delay of a normal distribution of mean 4 minutes with a deviation of 1.

The parts leaving this process have a 10% probability of failing inspection. What I want to do is decrease this probability of failure by increasing the mean time of the process, but I can't seem to work out any correlation between the process time and the failure probability.

Is it as simple as saying that a doubling of the process time i.e. up to 8 minutes, would halve the failure probability down to 5% or do I need to be looking elsewhere with this?

Many thanks in advance.