With the help of @Risk for Excel from Palisade Inc we are able to consider all possible outcomes of our project. But not just that. We will also know the probabilities associated with all outcomes. That is very powerful message.
Note standard ‘what if scenarios’ do not produce any conclusive outcome. Because, this not just one variable that changes, all variable do change within their ranges and frequencies. Also some variables may be correlated what was omitted here.
A simulation with @Risk is represented by number of interactions. An interaction is one outcome based o given set of variables. We can set the number of interactions and the number of simulations. Each set of variables is randomly selected. The whole process; selection variables, computing each outcome and summarizing all outcomes is referred to as the Monte Carlo simulation. The end result produced is in form of probability distribution and associated with it statistics.
That provides us with comprehensive information on what can happen with our project, enabling informed decision. For example, assume the NPV analysis can produce outcome as on this picture.

The outcome of our NPV analysis shows us all possible scenarios our project can deliver. Should we go for it depends on our attitude towards risk.
Most people would not mind to bet on heads and flip a coin when $1 is at stake. The chance to win is 50%. But how many people would play this game with $1 million? Not many. In general more money we plan to invest then greater security we want to have. But this is still individual decision. On the picture above we see, about 99% of all outcomes are above our minimal expectations, what is when NPV is equal zero. Possibility for negative NPV exists but is associated with very low probability. It appears to be attractive project.

