Effective Project Management: Traditional, Adaptive, Extreme, Fourth Edition

Chapter 5. Estimating Duration, Resource Requirements, and Cost

Round numbers are always false.

—Samuel Johnson, English critic

Figures are not always facts.

—Aesop, Greek fabulist

You get more control over estimation by learning from evolutionary, early, and frequent result deliveries than you will if you try to estimate in advance for a whole large project.

—Tom Gilb, Principles of Software Engineering Management

Estimating Duration

Before you can estimate duration, you need to make sure everyone is working from a common definition. The duration of a project is the elapsed time in business working days, not including weekends, holidays, or other non-work days. Work effort is labor required to complete a task. That labor can be consecutive or nonconsecutive hours.

Note

Beginning with this chapter and continuing through Chapter 11, I drop the use of the term "activity" and replace it with "task." At this point in the planning process all of the lowest-level activities in the WBS have met the completion criteria and are therefore called tasks.

Duration and work effort are not the same thing. For example, I had a client pose the following situation: The client had a task that required him to send a document to his attorney, where it would be reviewed, marked up, and then returned. He had done this on several previous occasions, and it normally took about 10 business days before the document was back in his office. He knew the attorney took only about 30 minutes to review and mark up the document. ...