Estimating Software

 

Organisations have to estimate continually in response to various internal and external stimuli. Business change is brought about by completing projects. To enable IT to play its part in improving an organisation it is necessary to be able to predict the costs and timescales as early as possible in the life of a project.

 

 

Standard Industry Practice

 

Do you know?

How big is your finger?

What is the Wind Direction?

What is the Ambient Temperature?

 

Predictable Costs & Timescales

 

It is now possible to use simple techniques to predict development costs early in the development lifecycle.

 

The Estimating Process (for more details email mbm@lalcrest.co.uk)

 

How big are the requirements?

Function Point Analysis

If the requirements are not yet sufficiently defined use one of the following alternatives:

Ten Questions

Number of Entities

Fast Function Points

Use Case Points

How much will the requirements creep?

Projects expand because the requirements are not fully understood before detailed studies are undertaken. This process makes allowance for project growth.

 

It is important to differentiate between project growth and change of project scope. If the in scope requirements change then the project should be re-estimated.

 

How much effort is required?

Use the regression from past projects

How long will the project take?

Use the formula from Barry Boehm's COCOMO model 2.4 * Staffmonths ^ 0.34

What is the effect of external constraints?

The effort to develop a project can be much influenced by external constraints. It is possible, for example, to predict the effect of shortening project timescales.

Improving Estimating

 

It is important to realise that any estimating technique is cyclic. At the end of a project it is vital to record what the project actually achieved.