Estimate in ranges: worst case, most likely case, best case for a task.

Compute expected case using the PERT formula: expectedCase = (bestCase + 4 * mostLikelyCase + worstCase) / 6

The pessimistic version of the formula is expectedCase = (bestCase + 3 * mostLikelyCase + 2 * worstCase) / 6

Related:

• Estimate tasks
• Create non-function requirement with a range

References

‣

‣ Use PERT, not a single number even for small-scale estimations, particularly in unknown area.