Page 129 - DCAP304_DCAP515_SOFTWARE_PROJECT_MANAGEMENT

Unit 6: Effort Estimation

Notes
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Caution Where certain options are available, PL/PM should ensure that everyone involved
are properly informed regarding the possible decisions so as to arrive at a feasible and
optimistic solution.

Tracking and Reporting Estimation Activities

Comparing planned versus actual estimates over time allows the PL/PM to see how well they
are estimating and also to see how their project is changing during project execution. If estimates
are never tracked, it is not possible to determine how good the estimates were. The estimation
work sheets should form a database of estimates.
This database can be used by the PL/PM to either calibrate estimation models or for purposes of
comparison when performing estimates for future projects. Estimation data, both planned and
actual, should be provided to the PKB for the benefit of other similar projects.

6.3 Estimation Basis

Project work estimation has three phases: the initial first cut, commonly known as SWAG
(scientific wild-ass guess), tracking the estimate against the actual numbers, and using the schedule
to see what’s happening in your project.
If you’ve been assigned project estimates, or if your project estimates aren’t particularly close to
reality, don’t fret. Try these techniques to make and learn about your estimates.

6.3.1 Phase 1: Create an Initial Estimate

If you’re a project manager, you probably try to estimate the work at the beginning of the
project, even if you’re assigned a project end date. Sometimes senior managers have trouble
hearing what you’ve said in your estimate. I use one of these three alternatives to creating
estimates for the entire project:
1. Provide a date range for the estimate: “We’ll be able to release between May 1 and June
15.” Some senior managers can’t hear the second half of that statement; they only hear
May 1. If you work for a manager like that, try either of these other two suggestions.
2. Use the word about to describe the precision of the estimate: “Five people for about nine
months or 10 people for about six months.” You haven’t described an end date, but you
have explained the resources you’ll require.

3. Provide a confidence level to describe the range of dates: “We have 90% confidence in June
1, and 100% confidence in Aug. 1.” In my experience, even the managers who can’t hear the
“between” estimate can hear my confidence levels.
Once you have a gross estimate at the beginning of the project, you can drill down and create
estimates for each of the project components. Whether you try to create precise estimates or
choose to use slack buffers to deal with incomplete estimates, you will have some project
estimate total.
The problem with estimates is that they are guesses. They’re the best guesses we can make, but
they’re still guesses.

Notes As the project unfolds, you’ll be able to acquire feedback on how well you estimated
using the second part of estimation, the EQF, or estimation quality factor.

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