"Program Evaluation and Review Technique (PERT) offers an effective way to convert estimates into probability distributions suitable for the business team and for the managers."
O : Optimistic Estimate.
Everything goes as planned, nothing as come into the way.
N : Nominal Estimate.
The value with the highest probability.
P : Pessimistic Estimate.
Everything goes wrong, very low percentage of chance to append.
With these 3 values it’s possible to describe the probability distribution of the task with the following formula:
µ = (O + 4N + P) / 6
Mu (µ) gives us the expected duration of the task. But this is just an average based on some coefficients and cannot be used as a deadline, it is a hint. Moreover the pessimistic estimate high value increase this average.
σ = (P – O) / 6
Sigma (σ) represents the standard deviation of the task. It is a measure to specify how uncertain the task is.The higher this value, the higher the risk.