Three Estimates used by PERT

PERT is a three point activity estimating technique that considers estimation uncertainty and risk by using three estimates to define an approximate probability for an activity’s cost or duration. The three estimates used are:

Most likely (M) - The cost/duration of the activity, based on a realistic effort assessment for the required work and any predicted expenses.

Optimistic(O) - The activity cost/duration based on an analysis of the best-case scenario for the activity.

Pessimistic(P) - The activity cost/duration based on an analysis of the worst-case scenario for the activity.