Hi Bad weather causes delay and additional cost. An analysis shows that certain bad weather conditions occur 8% of the time and cause work to stop. The range of bad weather weeks per annum ranges :- Min=2, Mode=7 and Max=9. The chance of bad weather is 100% quantum is the issue. Can you have a risk with aP()=1? How do you quantify the P() of a storm that is 1 in 50 or 1 in 100 years in probability terms? Ryan

Hi It depends on how you define "bad weather", which includes a specification of how bad for how long. You appear to have three different definitions in mind: 1. A "bad weather week", which is an event that stops work. (This happens in roughly 8% of weeks; or somewhere between 2 and 9 times a year). 2. A "bad weather year", which is a year containing at least one bad weather week. (the probability of a year being a bad weather year is presumably near 100%) 3. A "really bad year", which we don't have a deinition for (but we know that its probability is 1/50 or 1/100). Presumably it features a week with weather that is far worse than a mere "bad weather week". James