Estimates, Targets, Commitments and Plans

The first step in order to make good estimations, is understand clearly the difference between estimates, targets, commitments and plans:

Estimate

A statement of probability, a prediction, a tentative or preliminary calculation of the cost of a project.

“The new online shopping features, with the three people available, has a 75% chance of being completed by Oct. 15″

Target

A description of a desirable business objective.

“We want the new online shopping features live by Oct. 15″

Commitment

A promise to deliver defined functionality at a specific level of quality by a certain date.

“We commit to finishing the new online shopping features by Nov. 20″

Project Plan

A statement of how and when a project’s objectives are to be achieved, by showing the major products, milestones, activities and resources required on the project.

“The plan for the new online shopping features is:
– 1st sprint: 30 days, two people: prototype+proof of concept
– 2nd sprint: 30 days, three people: user histories 1, 2 and 3
– 3rd sprint: 30 days, three people: user histories 4, 5″

 

Summary: An Estimate is for decision support. Numbers without probabilities aren’t Estimates. We have to take into account that our estimates don’t become commitments; they are two different things.

Depending of how different are the Estimate and the Target, the Project Plan will need to account a different level of risk. The more the gap, the bigger the risk.

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