Introduction to Software estimation

Introduction to Software
Estimation

Estimation is done in terms of

* Size
*
Effort
* Schedule
* Cost

Size estimate

This is the
first estimation task. A measurement that tells the user what the system shall
do. Size estimate is usually done by Function Points Analysis, Feature points,
Use Case points or Lines of Code (LOC). 

Effort
estimate

The estimate for the manpower that is required
for a project. This is a most important factor determines many crucial
decisions.

Measured in terms of : person-hours, person-days,
person-months, etc. The popular effort estimation methods are:

size=2>* COCOMO 81
* COCOMO II
* Putnam’s Software Equation
*
Felix-Watson
* Bailey-Basili

Example:  If requirement is to build a web based system with
Login mechanism. The Size Estimate in terms of LOC may come to 150 Lines, and
Effort estimate would be 8 person hours.  Hence Effort estimate is
dependent on size estimate.

Schedule estimate 

This
is the duration between the start of the project and the end of the project
Often effort estimate are revised to meet the customer imposed schedule
Represented in terms of : Calendar-months, calendar-days, weeks, etc.

Cost estimate

A
major driver of cost estimation is the manpower cost (based on the estimated
effort)

Other costs include : travel, communication, facilities, project
specific training , hardware and software costs for the project team, etc.

High Quality & Productivity (Q&P) reduce the cost and minimize the
schedule of a project. Q&P are the twin aims of a project. Hgh Q&P can
be maintained by employing good processes.