  Accurate software cost and schedule estimation are essential for software
project success. Often it referred to as the "black art" because of its
complexity and uncertainty, software estimation is not as difficult or puzzling
as people think. In fact, generating accurate estimates is straightforward-once
you understand the intensity of uncertainty and framework for the modeling
process. The mystery to successful software estimation-distilling academic
information and real-world experience into a practical guide for working
software professionals. Instead of arcane treatises and rigid modeling
techniques, this will guide highlights a proven set of procedures,
understandable formulas, and heuristics that individuals and development teams
can apply to their projects to help achieve estimation proficiency with choose
appropriate development approaches In the early stage of software life cycle
project manager are inefficient to estimate the effort, schedule, cost
estimation and its development approach .This in turn, confuses the manager to
bid effectively on software project and choose incorrect development approach.
That will directly effect on productivity cycle and increase level of
uncertainty. This becomes a strong cause of project failure. So to avoid such
problem if we know level and sources of uncertainty in model design, It will
directive the developer to design accurate software cost and schedule
estimation, which are essential for software project success. However once the
required efforts have estimated, little is done to recalibrate and reduce the
uncertainty of the initial estimates.
