Balancing a project portfolio with ten projects that can be arranged in five different ways will result in 120 possible portfolio configurations. This is far beyond what intuition and gut feelings can handle, and this is why we need quantitative techniques to complement business acumen. As with any other stochastic model, the results produced might not always be right, but they will be right most of the time. Or, in the words of Jay Forrester , "There seems to be a general misunderstanding to the effect that a mathematical model cannot be undertaken until every constant and functional relationship is known to high accuracy. This often leads to the omission of admittedly highly significant factors (most of the ‘intangible’ influences on decisions) because these are unmeasured or unmeasurable. To omit such variables is equivalent to saying that they have zero effect. Probably the only value known to be wrong".