The major effort occurs early in the inception phase; thereafter, at the beginning of each iteration (see Activity: Refine the Development Plan).
Estimation should ideally be based in the organization's own experience, which is then used to calibrate an estimation
model, such as COCOMO. (See [BOE81] for a description
of the original model, or go to http://sunset.usc.edu/research/cocomosuite/index.html for the latest work.) If the Project Manager
is starting from scratch, using default values for model coefficients, it will be important to use other methods to
validate the estimates. Just as important is to obtain staff and other stakeholder agreement that the estimates are
realistic and achievable. However, the Project Manager has to take into account the experience of staff giving feedback
about estimates. More junior staff may be just guessing numbers and then adding large margins for error; conversely,
their effort estimates may be naively low. The Project Manager must be circumspect when dealing with estimates from
junior staff, and be prepared to counsel them when necessary, and offer the assistance of a more experienced peer. See
Task: Plan Phases and Iterations for more information about
All enclosed plans and sections of the Software Development Plan should be evaluated through internal walkthroughs and
reviews before the Project Planning Review occurs.