3 - Point Estimation (PERT Sigma Calculations)

The PERT Three Point Estimate technique is a type of three point estimate.  The only difference is that it applies weighting so that the most-likely estimate is weighted 4 times more than the other two estimates (optimistic and pessimistic). This formula is most valuable in estimating time or cost of activities for projects that are especially unique, such as in research and development where there are many unknowns.  For projects that are similar to previous projects and there is good historical data and expert experience, the formula is less useful because you could use other techniques like analogous estimating (based on previous experience and projects).